Severe lick granulomas, please help :(

It's because he has separation anxiety. He started doing it in June, when I started moving for college. He's living with my grandparents (whom I lived with) and then he'll be moving up with me in about a month. I know he isn't on the best food, he's had food allergies his entire life, but he hasn't had a problem with Beneful ever. I don't know if I can afford the better options..

What would you suggest?

I think I'll look into Iams, it seems to be the cheapest. I checked all the prices for the other brands, and everything is so expensive. I cleaned his sores with witch hazel and put some GoldBond on them. I have a friend who swears by coconut oil, as long as the dog doesn't have the ability to lick at them. The biggest problem now is that because I'm moving, when I'm out of town, my grandparents don't do more than the basics of food and water, and Buddy is forced to always be outside. They don't think his paws are a problem, and there's no way they will get down on their hands and knees to clean his paws everyday.

I'm not sure how to keep the granulomas dry.. The goldbond powder didn't seem to help. At least not on the worse paw. I keep patting the worse one dry because it's wet and I don't know what else would work