Hi April,
I think he has probably had more vaccines in the past given that he is 6 years old. So I am with you on this one, forget about he vaccine for now.
Forget about x-ray and antifungals and save the veterinary bills for now, just give him lots of TLC and good natural food and see whether he improves.
Do not forget to add omega 3 source to his food and teaspoon of coconut oil to his food. You can also apply coconut oil on the affected place on the skin.