ITunes skips songs, when import to iPhone all songs are 2:34 length (they aren't)

Question

So my iTunes and iPhone are completely FUBAR and I can't find any solution.
I have an iPhone 4s on version 7.0.4. I am currently using iTunes 11.2.1. Late 2011 Macbook Pro running 10.8.5, whichever cat that is.
Starting in December 2013, most new songs I import into iTunes will skip at random points in the song to the end of the song. There was no pattern as far as I could tell, though it didn't seem to be happening with music bought from iTunes. Music from CDs, bandcamp, etc. was the problem. For example, a song with a length of 5:55 would randomly skip to the end at 3:46. But, if I manually skipped to any point after 3:46 it would play the normally skipped part fine.This was not a huge problem as I could then import the songs to my iPhone and listen on there with no skipping.
In the past few weeks though, now every song I import to my iPhone cuts off at 2:34. Every single song. They skip in iTunes at a random point, then I import them to my phone where they skip at 2:34 (and are labelled as only 2:34 long), and then after being imported to my iPhone they skip at 2:34 in iTunes as well.
Last night, for absolutely no reason, about 80% of my music disappeared from my phone. It's still there, but can't be played for some reason. So I tryed syncing to my computer, but lo and behold, every song on my iPhone is now 2:34.
Please help, I'm very close to burning all of my devices in a fire and starting over.

Answer 1

I also have this problem, but on my 64-bit Windows 7 desktop. My income level no longer permits me to purchase Apple computers. Anything that I've bought off of the iTunes store, most of it's ten to six years old, will not play any further than 2:34. I just knew when I agreed to this "protected music" business I'd find myself a decade down the line staring at an expensive but unplayable music collection.