My cat , Rocky, is 14. I also have to muzzle her when we take her to the vet. He is able to take the muzzle off after a little bit. But I hate to stress her out any more than possible. Rocky also had hairballs and would vomit like your cat . If there is hair in the vomit to me it sounds like there is a hairball Sash is trying to get rid of. Do you ever give him Hairball Remedy? Gel in a tube to help the hairballs along. Can find it in any petstore. Recently I switched to all Canned food for my cat and she doesn't vomit or have hairballs anymore. If you are worried, I would call the vet and explain what is happening and that you don't want to stress Sasha by taking him in unless necessary. The vet should be able to tell you what to try or if they think he has to come in. I've called my vet quite a few times and they've been happy to try and help me over the phone first.