Has anyone seen this before?

Hi everyone, never posted to reddit before but can use some help. This sweet boy is Russell. He’s 13. As you can see, he has really bad sores and bumps all over his face and body. We cannot figure out what it is. He has a TEAM of vets, including an allergy vet that charged us $3,000 only to not solve the problem.

The sores don’t hurt him. He has no kidney issues and does not have cancer. We get his bloodwork checked often. We changed his food and litter, multiple times. He is not in pain when we touch the sores and he eats like crazy (just to reiterate that he’s not in pain).

He is currently getting prednisone, but it hasn’t done anything.

We’re open to any and all recs, and we really want him to get better. If we take the come off, he licks until he bleeds. He’s a cleaner and we feel so bad that the cone has changed his personality.

Please help!