Bassets with IBD?

My 1-year-old boy was just diagnosed with IBD. For months, we’ve been in and out of spells of vomiting and weight loss. Bloodwork, stim test, and ultrasound all ruled out more common issues. Finally an endoscopy revealed it was IBD all along. Trying to avoid steroids as my vet warned me when used this way could cause a list of side effects, including diabetes. We’re on a hydrolyzed diet (likely forever) and he’s been having Hills kibble and the Royal Canin hydrolyzed treats. He used to wolf the food, until the most recent slump. Now it’s pulling teeth to get him to eat, but he’s wolfing treats. I’ve tried warm water, burying treats in the food, etc. etc. Anyone have any suggestions or going through the same thing? He could definitely benefit from putting on some weight, so want him to love his food! TIA!