Have you ruled out external parasites for the itching? (ie, fleas) Get him on a good food. If you can't get to a specialty store but you have Petsmarts in your area, try something like Blue Buffalo. (Going to a rich food, he may have some diarrhea while you transition him over to it, but give the new food a chance to work its magic.) Add a little bit of olive oil or fish oil to the food; those are good healthy fats and good for the coat. He would probably benefit from a good medicated bath, too. But if you take him to a groomer to have it done, wait for him, don't leave him there. (Some groomers, like the shop I work for, wont take unvaccinated animals unless they're straight in and straight back out while the owner waits.) Be very, very careful about taking him anywhere that other dogs frequent. His immune system is probably compromised and you don't need to add on to that with other problems like Parvo. When you take him to the vet, carry him. Don't put him down on the floor where he's more likely to be exposed to yuckies.
The oil, good food and bath are the only things I can suggest to start. That and find another vet that can see him quickly. The wound on his face is not that horribly bad. Keep it clean and draining. If it scabs over, gross as this sounds, pick the scabs off so the pus can drain. If the vet gives you an antibiotic, make sure you use all of it.
Disclaimer: I'm not a vet and have no training in that field. Just sayin'.
