My super sexy husband fixed my database
Apparently Macs have a built in sqlite command line tool and husband was able to dump database to a text file and recreate it from there
He also found a couple of culprit books... No idea if I'm able to sign out now, but I don't really want to try
So now I can get to puzzling on why some book covers aren't showing. Any idea on whether I need to delete a book with Calibre before re-sending it to the device if I made any changes with Sigil? Edit: apparently not, same thing I tried before worked perfectly this time now the database doesn't have its knickers in a twist
Also still interested to know about question 3, for future reference or for when I'd like to cheat my statistics...