Um.. NO. Do not give cats milk. They are lactose intolerant and it will just give them diarrhea. He does not need to be having diarrhea and getting dehydrated. That will make him VERY sick.

I would find a different vet, the kitten NEEDS a proper deworming and waiting won't help him. He's just going to get worse.

The canned food generally doesn't have any nutrients at all, it's just fatty and watery. Get some high quality dry food and soak it for a bit in water and see if he'll take that. Canned food is generally only for a treat.