hows it going feeding with the syringe feeding?? I always find the syringe blocks because the powdered rescue food sediments separate in the syringe a drop or two of a fruit baby food fill help the food flow better. People might think this is not important but when he are fighting to keep bunny sat in the right position with a cloth bib round there neck to catch food, the last thing you want is the syringe sticking. Also a nice drink of water after the feed to good.
Has bunny had a steroid shot yet to increase the appetite, there was one type which really worked on my bunny I could look through my records if you need know which one, better try one that you know works well on bunnies.
Let me know