Just to update:
I unarchived some of the much older issues (dated from September) in the hopes that once they were unarchived, I could manually delete them from my library online (via computer). But even though they are existent on my nook (including at least one that I've downloaded and opened!), they still appear nowhere in my nook library online. So I CANNOT delete them. I've even tried manually deleting them via my computer, but they just appear in the list ready to download again when I recheck.
Most people have problems getting books they want ONTO their nooks. I can't seem to get this old crap off of mine.