Hmm, i think i understand what is going on.

Its a shame you had to delete all that off of it. But i think that if you want to get rid of it, a system refresh/restore would do it best. You see if i was there i could look and see where these big files are and sort it for you, but it turns out that i'm not.

My suggestion before you do a restore on it is to plug it in and then go into "My Computer", then into the device folder which is the iPod, then hover the mouse over the folders and see which carries the most amount of memory, then you can narrow it down per folder until you find the big files which are taking up the memory. For something like this to happen it is unlikely the files would be scattered, just do it step by step to find the folder with the biggest amount of files in it and you should find the huge file. If you find a folder of files or a big file, report back and tell me, i'll tell you if its delete-worthy.