He's around 550 grams, maybe a little over that. I wasn't weighing him regularly before the winter fast so I don't know if he's down from before that or not. But it's definitely not the size of the prey putting him off, he was regularly eating thawed rats quite a bit larger than the mice he's getting now.

Yes, I've generally continued to feed him in a separate enclosure since pretty much since we got him, because I didn't want him to associate us coming and opening his cage with food, and getting into that predatory, pre-strike mindset when we might just want to take him out. That seemed a lot more important back in the days when he was always quick to hammer meals, and once almost bit me before he noticed I wasn't a mouse and pulled back in time. When he got picky I hoped that going into the feeding enclosure would help stimulate feeding, just from the conditioning of him always having gone there to eat - that it would activate predator mode. But I've also tried leaving thawed mice in his cage and had him reject them, only to try bringing him to the enclosure and having him readily take something live. Home tank, feeding enclosure, whatever variables I change, the only deciding factor in whether he eats seems to be is it live, or not?

So far what I'm hearing is, keep a close eye on his weight, and of course on husbandry, and as long as he isn't losing too much body mass, then just wait him out? Just keep offering thawed and nothing else, until he gives in and eats, no matter how many months it takes? How much weight would he have to actually lose before I knew to abort and just feed him what he's wanting? I'm a little scared to try this, it feels like an extended, slow-motion game of chicken to me, with only my snake's life on the line.