Update: he is still among the living! Been doing pedialyte soaks and still letting him have a water bowl big enough for him to soak himself in his tub. He's put on another 9 grams in water weight the past 2 day. He's like a little sponge.
This afternoon is the first time I've seen him out of his bowl and in his hide. He's chilling on the cool end. But I've got the ambient in the room at 80 ish during the day and down to around 70ish at night.