The best thing you can do for your dog is completely avoid the advice of clunks, cranks, eco-freaks, and vegetarians! In case you hadn't noticed, dogs are carnivores and can live on a diet of small game -- if they eat the entire captured animal.
Look to your vet for answers, not to clatterbrain vegetarians on Yedda.
If your current vet lacks an answer, then talk to another vet. Do not tell the next vet about prior veterinary treatments as the prior vet may cover his behind at your dog's expense -- they can be that unethical.
IAMS dog food (as prescribed) might be your best bet. Also, treat the scabs much more aggressively: demodex or sarcoptic mange can present in patches. Heart worms (micrifilaria) can present as skin lesions also -- when they clump under the skin. If you have a simple bacterial infection, wash it daily with iodine soap, and once dry, coat with antibiotic salve. Install a "cone collar" to prevent the dog from licking off the medication.
If none of this works, consider the unthinkable: might your buddy be in such misery that he'd want to get it over? if so, humane euthanasia is the humane option.
If so, talk to the humane society and adopt a new buddy.
www.iams.com
