Maybe I should try the tub for a while until he eats a few times, then place him in his tank in a dark room and work from there? Either way, I'd like to change the substrate because I know humidity has been a consistent problem, so, that's getting done today. He's going to end up in some sort of dark environment by the end of the day... and I am going to attempt to feed live by next weekend after he's had this week to readjust.
The vet that told me about the baths got her info from a herpetology forum for vets. I don't think she was a specialist; she seemed to know less than I did. I am taking my kingsnake (Tigger) to a new vet today. I'll run the history past him and see what he has to say, too.