Hydrolyzed food feels like a punishment

I have a Siamese cat who has inexplicably thrown up two or three times a day, two or three days a week, for years now. Sometimes it's shortly after eating, sometimes it's hours after eating, sometimes it's his wet food, sometimes it's his dry food. No vet has ever been able to explain to me why it would be happening, but clearly it's concerning... we have tried novel protein foods, raised bowls, hairball foods, straight up "better" quality foods... To no avail. There was never anything remarkable on his bloodwork or any obvious reason he'd be so vomity. He is not a particularly picky eater, thankfully, and loves steamed veggies and pumpkin and the like. We have been told it may be anything from a food allergy to IBD to a fluke.

Today at his dental cleaning, his pre-procedure bloodwork indicated a "barely elevated" amylase (at the high end of normal) which they explained is an enzyme that, when elevated, can indicate kidney dysfunction. Since he's had gastrointestinal issues in the past and this history of vomiting, we agreed to switch him to a hydrolyzed protein diet to see if it helps the blood values as well as the vomiting. What I didn't realize is there are basically no wet food options or treats that he can have on his hydrolyzed diet..... They told me to soak his kibble in water and mush it up if he wants wet food. I'm thinking about all the churu he will miss out on, all the treats he loves that he'll never get again if this hydrolyzed diet turns out to be the solution to his problems.

Am I overreacting? This feels like a potential life sentence to Boring Food Town and it makes me feel so guilty - he loves food!

Ultimately my question is (and yes I do plan on posing this question to my vet tomorrow but they are closed now and I also am hoping to hear some anecdotal experience from someone else who has been here) : can cats have "real" food while eating a hydrolyzed protein kibble? I'm thinking the steamed veggies he loves, pumpkin, the occasional small piece of cheese or grilled chicken.

And further, if he's eating a hydrolyzed protein diet for 99% of his calories, and he has a half a churu or two greenies treats that he adores, will that REALLY counteract all the effects of the hydrolyzed food?

IF this happens to be the solution for him, and he's feeling better and vomiting less, I obviously want to keep him on it. But I'd also love to be able to still give him some joy and variety in his diet if I can safely do so. Does anyone have any thoughts or advice?