Goood luck with this little guy, so sadIs that muscle??? Geez. Like you said, he is in shed, so I wonder how that will go over the spot in question :-/
I hope he pulls through.
Unfortunately a lot of vets are like doctors. No specialties and generalize all cats and dogs and don't know a lot about small animals. Yuck. I always have issues about feeding with my vets because they go with big name brands that pay them to advertise and the nutritional value just ISNT there. This is no better, in fact its much worse. To just rip off a mouse trap when I could have thought of many better ways to remove it despite the fact that I only went to school to be a vet for 2 years before changing my major.