ipod wont sync entire library

So i have almost 6000 songs in my itunes. I mistakenly moved the folder titled "itunes" from the music section in my finder to an external hard drive trying to save space. I realized immediately that this would make the songs unlistenable and moved the folder back from the external hard drive to the exact same place I took it from in the finder. Now most of the album artwork has dissapeared, and it cant find any of the artwork (even albums that i previously got album artwork for in this way). Also, when i plug my Ipod in to sync it only syncs ~800 of my 6000 songs. All of the songs are still in itunes, and are listenable. The songs that do sync seem super random (1 or 2 songs from 5 different albums for some artists). Does anyone have any idea how i screwed this up and if there is a way to fix it? like i said all of the music is still in my itunes library but the artwork is all gone and it will only sync ~800 of my 6000 songs.