Then he is starving and pukes, no

Something else that happened that my family thinks may have affected him, when he was a kitten we left for a couple days and he shut himself in a room and had water off windows but no food, and I think that may have affected him

I would try slowly weaning him off so he does not eat as much.

We've been waiting for him to lose some before we do that, but he just isn't and we've tried weaning him off and he just starts puking again

Honestly, I'd take him to the vet and have him checked for kidney disease. It's exceedingly common in cats (and why wet food is becoming highly recommended over dry) and it's very rare not to have an older cat who doesn't have some sort of CKD.