Encountered just about every issue possible trying to sync music to iPod Touch after 8.1

Question

If you're having any sort of syncing problems after the updates, bear with me as I tell my tale. Hopefully you can find yourself relating.
I have an fifth generation 64gb iPod Touch. Ever since I've updated to iOS 8 (then 8.1), I'm beginning to look at it as useless. I know there are all sorts of threads out there about people having difficulty syncing their music after the update, and I'm probably not covering any new ground, but I thought it was worth reporting every problem I've encountered and all the fixes I've tried.
I have a large music collection. Around 7000 tunes. They're all safe and backed up to my iTunes library on my MacBook Pro. I was aware that updating the iPod to iOS 8 might cost me a considerable amount of storage space, so I did it cautiously. I did it through iTunes, and I had no real issues. It didn't take up the huge amount of space it did for others. But my music collection on the device became all sorts of screwed up. Suddenly I was missing entire albums and artists. What albums and artists were still there often only had the first track of the album. Many songs were kicked off the device itself and I had the option to download from the cloud (I assume that's what that button meant). For about two weeks, I was too busy to listen to music, so I put the problem out of my head.
Last week I finally decided I needed to get around to fixing it. I plugged it into my USB port, and iTunes told me I was 20+ gb over capacity, with the 'Other' bar taking up most of the storage. I only had a few photos and apps on my iPod, but I deleted them anyway. I started going through my iTunes library and haphazardly deleted albums I figured I could go without. None of this even put a dent in getting more storage space. I quickly realized that I still needed to update my MacBook to OS X Yosemite, as well as get the accompanying iTunes update.
After the (justified) hours and hours of updating everything (absolutely everything I'm discussing is on the latest update), I plugged my iPod back in, and surely enough, the capacity bar reflected the actual amount of music I had. I had a good nine or ten GB to spare. 'Other' was barely taking up any space. I was elated, so I clicked sync. iTunes quickly jumped to either Step 4 of 4 (Waiting for Changes to be Applied) or 5 of 5 (Preparing to Copy Items) and hung. I gave it close to 45 minutes, and nothing was transpiring. I tried over and over. I'm not syncing via wi-fi (although I did try that). I'm syncing manually. I tried every permutation possible. Syncing only checked artists and albums (checking all those artists, by the way, takes a good fifteen minutes), syncing the entire library. Everything. After reading about people having similar issues online, I decided I may as well reset my iPod completely and set it up as a new iPod.
Again, I don't use my iPod for photos or apps, so I'm not having to worry about losing anything in the process of resetting. There's no need to restore from back-ups- all my music is in the my iTunes library. I don't really "do" iCloud, and any restore points on my computer are automatically done and unnecessary. After resetting, I tried to sync. Again, straight to the last step of the syncing process. I was patient, but clearly nothing was going to happen. I must have reset my iPod and set it up as a new device about five times. Finally, I got a sync to seemingly start working. I watched as all my music started turning black in the 'On My iPod' screen. I periodically checked the device itself, and noticed that, arbitrarily, I was only getting random tracks from albums, often the first track (for instance, I have every Beatles album, but I was getting one track per album on the device). When it finished syncing, I clicked on the tunes listed under 'On My iPod,' and found that many of them popped up with an exclamation point, indicating, I assume, that the song was unable to sync.
I reset again. Multiple times. Trying everything. I finally decided to sync only checked songs, and I checked one artist (embarrassingly, ABBA). Surely enough, the full ABBA album synced fine. I slowly started checking more and more artists. It was working. I got all the way to the bottom and watched as everything started syncing as it should. Entire albums were showing up on my device. Half an hour later, everything was synced, and I couldn't have been happier. I disconnected the device and went to listen to some music, only to find that everything was gone. Everything that I just watched sync perfectly to the device. I had no content on the device. Nothing at all. I reconnected it, and suddenly I was grossly over capacity again (I wasn't at all when the sync had finished). The bar did not, at all, reflect the contents of the device (in fact, I had nothing on the device at this point).
More resets. Again, I would get either no syncing at all, or only getting one or two tracks from artists. Finally, I called Apple Support while it was syncing again to explain the problem. The man said he's been getting vaguely similar reports. I told him that it appeared to be syncing properly as we spoke, but that I was confident I would lose all my music again once the sync finished. He stayed on the line, and bizarrely, out of nowhere, it synced perfectly. I disconnected the device, and I had a fully functional iPod again. For the past week, I've had no issues with it. After this successful sync, by the way, I was told I had 8.7GB of free space, which I would call accurate. The 'Other' was hardly there.
This morning, I added some new albums to my iTunes library, so I connected the iPod and clicked sync. Nothing. The new songs showed up on the 'On My iPod' screen, but they were greyed out with the loading circle. I waited an hour as it hung at 'Waiting for Changes to Be Applied' or 'Preparing to Copy Items'- I forget which, but I became accustomed to both. I was only adding maybe fifty new songs, but no progress was being made in terms of syncing. They remained greyed out. Not wanting to reset the iPod, I called Apple Support again. The man remotely accessed my screen and seemed quite puzzled. He saw the almost 9GB I had to spare. He had me click some of the obvious settings I'd tried time and time again. Finally, he had me, for a third time, switch from 'Sync Checked Songs' to 'Manually Manage Music and Videos.' He and I witnessed the capacity bar immediately change to 42GB over capacity! 42GB! He accused me of legitimately being 42GB over capacity (I'm not mad at him- he was very nice, by the way), and I pointed out how ridiculous that was. He agreed. After more and more troubleshooting, I told him it was a lost cause, and my only hope was to reset the iPod again. I realized that, from now on, whenever I sync new music from my library, I'm going to have to reset the device and sync from scratch. I got off the phone with him and did just that.
Two attempts failed, again hanging at those dang last steps. I was patient as can be, understanding how much music I had. An hour later, nothing. I tried once more, syncing artists slowly at a time, and suddenly, arbitrarily, it chose to miraculously sync perfectly. I walked away from the computer and iPod and took a long walk to clear my mind. I came back, and looked at the 'On My iPod' screen. Every song was black and on my device. I turned on my device, and... one track per album. When I clicked the songs that were allegedly on my iPod, I was getting exclamation marks, and they wouldn't play. The songs that sync and don't sync are entirely arbitrary and change every time. It's not a matter of corrupted files, I don't think. If it were, I would expect the same songs to be giving me the difficulties. The capacity bar offered an accurate reflection of what my device would be if everything were, in fact, synced. Even though only probably 10% of my library had made it to the device, iTunes told me that everything was synced and was taking up the appropriate amount of space. I disconnected the device, turned it on and off, quit iTunes, restarted my computer. I connected the device again, and the capacity bar now told me I had almost nothing on my iPod. I checked, and the iPod, once more, was devoid of content.
I have no idea what to do. I'm at a complete loss. I don't get it. I've tried nearly every fix that has been suggested online. I've tried all the different ways of syncing. I'm not syncing voice memos. I don't have any strangely titled tracks. I don't have any tracks that are unattributed to an artist or album. I have no duplicates. I have OCD, so my iTunes library, though vast, is kept in tip-top shape, and everything is ordered and tagged perfectly.
Wow. Hold the phone. I'm currently both overjoyed and even more flabbergasted. As I typed this long message, I left my device plugged into my computer. I didn't start a new sync- just left it plugged in. I happened to look at it just now, and, um, everything is synced. My iPod is working again. Still, this has become an ordeal that needs to be addressed. I'm scared to death of what will happen next time I want to sync new music to the device. I suspect more and more hours of resetting and fiddling with options. I want to stress enough that I'm positive this isn't a matter of me not being patient enough. Often times, I do indeed cut the sync short when no progress appears to be made, but I just as often leave it running for long periods of time.
This whole thing leaves me very on edge. Even operating the device scares me, because I'm getting excessive lags, and I'm worried that at any moment, the music will be gone again.
Anyone else going through this ordeal? Specifically these problems, or, like me, all of them at different times? Anyone randomly find that they're occasionally almost humorously over capacity? I'd like to hear your input. On my end, the only fix I've found is to just keep resetting the iPod as a new device over and over again until it eventually works properly. Again, this is pretty effortless (though time-consuming) for me, because I don't have any pictures or apps to restore. I use it solely for music. I can't imagine the stress of worrying about losing items other than music. Is this general and bizarre syncing problem just a bug that will eventually get fixed? Is Apple aware of it? When you've faced as many dead-ends as I have, it's hard to specifically articulate the problem to them. Can anyone relate or offer any fixes?
Again, using a 64GB fifth generation iPod touch updated to 8.1. 2GB non-retina MacBook Pro. OS X Yosemite. iTunes 12.0.1.26.
I also have a 64GB iPad 4, and I'm still debating whether or not to update it.

Answer 1

Kind of a similar issue with me.
I've got an ipod touch that I use for my music only.  The vast majority of what I have loaded in my iTunes library on my laptop is music I've imported into iTunes from my cd collection.  I have several albums that came from non-iTunes digital purchases (cdbaby, amazon, etc), and then guess a few hundred albums purchased from the iTunes store.
Everything seemed to work fine with ios 7 but once I upgraded my ipod to ios 8  I started having sync issues.  My problem seems to be isolated to music that I did not purchase from iTunes (which is currently most of my music).  I'll sync the ipod with my iTunes library on the laptop and I end up losing all non-iTunes purchased content on the iPod.  The albums still 'show' on the iPod screen but once I select one to play it quickly scrolls through all the tracks and comes back to the screen showing the tracks with the red circle.  If I go check the number of songs on the iPod in the settings>general>about option it will now have deceased the total number of songs by the number of tracks that were on the album.
I'm not a 'technical' type of user so everything I was trying to correct the issue was pretty much just change settings options in iTunes on the laptop and/or settings on the iPod without any real knowledge or confidence that it would help.
Eventually I gave up and deleted all content on the iPod and restart it as a 'fresh out of the box' iPod. It took several attempts at that to get all my songs copied from the laptop back to the iPod. After several attempts I finally thought it might have to do with the iCloud feature on the iPod (since it was only syncing iTunes purchased items and ignoring everything else not purchased via iTunes I thought it might be trying to verifying the items before actually loading them).
I completely set up the iPod again but used the option to not use iCloud (I don't use it to back up/store anything anyway). That attempt resulted in all my songs/albums syncing from the laptop to the iPod.  Everything seemed to working fine for the past few months but then it happened again the other day. I had purchased a cd and imported it into my iTunes library... plugged in the iPod to sync everything and it wiped out all the non-iTunes purchased content again.
I deleted all the content off the iPod and did the 'out of the box' setup again and everything synced. Then this morning I purchased an album off of iTunes, hooked up the iPod to sync and again, it wiped out everything except my iTunes purchases.
This is getting beyond frustrating.  The reason I've gone with apple all these years is because they are supposed to be 'idiot proof' for those of us that have a lot of knowledge of how/why all this works.