So they didn't do the neuter, right? Because I wouldn't put him through that in his condition.Then this last time I brought him in to be neutered and demanded they check him out really well to make sure he would handle the surgery and come out okay. They called me within 20 minutes of dropping him off, saying he is suffering from chronic malnourishment.
You are getting some great advise here. I hope you get to the bottom of this and he starts to improve. Sometimes you just have to keep nagging your vet or change vets. Which I know you did. I'm just saying. When YOU know that something isn't right and no one listens, it's time to change. You did right by listening to your gut. I mean, honestly, just looking at him I can tell he is in poor condition and I am far from being a vet. It breaks my heart! We all will be eagerly awaiting updates from you. Good luck and give him a big hug from all of us!