"This can't actually be one of the largest stocks of second-hand books"

Any library can be described as a second hand store of books and it seems this one is pretty large!

"I wish I could get rid of them all"

You could donate them to the really weird collectors - see OP!

I used to have quite a large collection of CDs (and tapes but they are mostly buggered). It took quite a while to rip them to FLAC but they now take up quite a small amount of disc compared to photos and the rest. A terabyte is not particularly large these days.

"terrorist pornographer" - that is quite a job title.