Sorry your little guy is having problems.
My little boy had problems with his tummy since I got him. He has a very sensitive stomach. I went through a few high quality foods including Natural Balance Duck. I was mixing his food with pumpkin and probiotics. No luck. He would only get better with Hill's Digestive I/D Prescription Food. I was happy, but I wasn't going to keep him on vet food all his life..
The vet is another story. I paid for 2 de worms, unnecessary x rays, sedations (so they can x ray him), exams, but nothing helped. They even suggested surgery because they saw "blockage" in his stomach. Unreal. Diarrhea would come back. They even tried diagnosing him with a food allergy and prescribed hypoallergenic food...
He was getting worse. Sleeping all the time, not eating, not playing.. I finally took him to another vet. They didn't see blockage. Only gas. They diagnosed him with a stomach infection. They gave him a shot of antibiotics and sent him home. I kept him on Hill's until he regained his strength and energy and switched him to Wellness complete health chicken formula. No more diarrhea. No more smell. No more stinky farts. One happy kitten.
Try testing different foods. I know Weruva is high quality, but my boy's stomach can't take it. I also had him on this and it helped.
https://www.chewy.com/vetoquinol-pro-pectalin-anti/dp/109720
I know how frustrated you must be. We all want our SVs to be healthy and happy. I hope you find a solution to his stomach issues.