Keeping only some music, or deleting playlists from device?

Question

Hi all,
I have 16 GB of music on my iPhone after I turned on iTunes Match.  I want to delete most of it, but there are some songs that I want to keep on the device.  This has been much more difficult than I thought.  I've been having this issue ever since I subscribed to iTunes Match when it was finally stable enough to work on my music library (about 10 months after subscribing, around 6 months ago).
The reason I want to keep some songs is because a large part of my music is in lossless format, and I listen to it on high quality audio systems and can easily tell the difference between 256kbps AAC and CD quality.  The CD quality sounds much better, and I definietly want to keep about 5 GB of music in this format on the iPhone, as I listen to this music even at home with my iPhone plugged into my receiver or over AirPlay.  If I delete my entire music library on the iPhone and download the songs again, they will be downgraded in quality.  I've done a lot of research about this, so I'm sure this is the case, unfortunately.
So now I have to manually delete about 1000 songs (out of ~1400) from my iPhone music library.  What's worse is that I have almost as many artists and albums as I do songs, the nature of the music genres I have - rarely are there albums or more than 2 or 3 songs from just one artist without it being a remix by another.  This means I can't just go through different arists or albums and delete the ones I don't want.  It has to be songs.  Plus I am not good with the names, so I have to listen to the song before I know whether to delete it.  The songs I want to keep are easier to identify, but unfortunately I can't just choose them.
I could create a playlist of all the songs I want to keep, but there is no option to delete songs from all other playlists.  In fact, there is no option to delete all the songs within a playlist, or even delete a song from a playlist itself!  All my music is organized by playlists, so it's easier to find the songs to delete by navigating through playlists, rather than the flat list of 1400 songs.  The only way to delete a song from there is to open the playlist, play a song, then click the top right icon to show the album where it will usually show just the one song (as I have about as many "albums" as I do songs), and only then can I swipe and delete the song.
This is a huge hassle, and I have been doing this to free up space on my iPhone.  I have about 32MB free, and before I can download an app, get an update, or even check my mail, I have to go and find more songs to delete through this method.  After deleting about 10 songs, I have enough space to continue using the phone for about a week or two.  But I just don't have the time to go and do this for 1000 songs!!!
When I plug the phone into the computer, I can see all the songs in iTunes.  I wish I could just select the songs (for some reason I can't change the sort order, which is a pain), and delete them.  But iTunes won't let me!
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I checked how long it's taking me with the current method.  I have 1400 songs (on the device) in 85 playlists, taking up 16 GB.  I want to keep about 350 songs, around 5 GB I'm guessing.  This is an estimate, because I only know which songs I want to keep when I hear them, or by which playlist they are in.  It's easier to find the songs that I want to keep, but instead I must to delete the songs I don't want to keep, as that's the only way Apple allows it.
It takes about 6 seconds to navigate to the song (on average, navigating through playlists), about 10-20 seconds to play it, and 3 seconds to delete it.  That's about 25 seconds per song.  With 1000 songs, that's 25,000 seconds = 7 hours of work!!  And that's continuously doing this, which isn't even possible as sometimes I get stutters or random freezes for a few seconds before the iPhone is operational again (background apps/notifications?).
Even if I could select multiple songs within a playlist, or use iTunes to delete, it might not be much faster.  Let's say it takes as long as 5 minutes to evaluate a playlist and select songs to delete from the playlist.  With 85 playlists, that would be 85 * 5 = 425 minutes = 7 hours!  Now if I could do it as fast as 1 minute per playlist, which might be possible with iTunes (e.g. it has Select All or allows you to delete an entire playlist on just the device, without affecting iTunes Match), it would only take 1.5 hours, which is reasonable.
But it's still somewhat ridiculous having to spend an entire workday just to salvage ~350 songs.  If I could "tick" and select these songs that I want to keep via iTunes, I think it would take me about 5-7 seconds in the worst case if I have to listen to the song.  I usually know the name of the song that I want to keep, so it would be faster, but even if it did take 6 seconds on average, that would be 6 * 350 = 2125 seconds = 35 minutes.  Now that's more reasonable!
If anyone has any suggestions to speed up or make this process easier, I'd really appreciate it.  Otherwise I'll struggle with waiting for a better solution while in the meantime spending 5-10 minutes deleting a few songs every week.  At this rate, I estimate I'll finish in 100 weeks.  This doesn't sound that bad actually, but it'll probably get more and more difficult finding the songs I don't want since there will be a higher ratio of songs I want to keep vs. not.  So it might be closer to 5 years (or I'll have to spend more than 5-10 minutes per session), at which point I'll hopefully have a 256 GB iPhone and don't have to worry about running out of space, especially with a measily 16 GB of music.  I'm tired of the running out of space warnings ever since I got my first iPhone (64 GB).
Thank you everyone!  For listening, and any advice you can give!

Answer 1

This is a good idea.  Somehow I forgot about it, as I haven't been using the computer I used to sync my iPhone with for like a year.  I stopped thinking about syncing when everything moved to iCloud.  However, I still do have access to that computer (sort of - it doesn't have a monitor right now), and more importantly the original music files that I want to transfer!  I remember this was my original idea when I first signed up for iTunes match and wrote it down somewhere, but forgot about this plan.  Probably because it took months to get the feature working in the first place.
I was scared to turn off iTunes Match once I got everything working, as I didn't want to go through all the hassle again.  So whenever I plug in my iPhone, it wouldn't let me manage my music.  It seems to be much more stable now, so I suppose I can just disable it on the iPhone.  I can keep it enabled on the computer, right?  Then I sync the playlists that I want, and it should delete anything not selected on the iPhone.  Hopefully once it's done and I turn iTunes Match back on, it'll go back to working smoothly.
Thanks, Michael.  I forgot about transfering the music from the original source.  I'm getting used to how powerful these iOS devices are nowadays that I forget you can't do everything with them, that more complex operations are better done on the desktop, but in a specific way.
I still think that iTunes should let you delete music straight off the iPhone when it's plugged in.  But that's another issue.