Hello and welcome to the forum. From the information you have given It sounds as if the vet has diagnosed chronic pancreatitis ie ongoing. As you probably know, the usual advice is to feed a low fat diet. David has written an article on the dietary management of pancreatitis here.
Additionally, we have a forum thread on the subject here.
Thinking about your budget, I am wondering if it might be cost effective to home cook for your dog. Have you given this some consideration? It needs to be done properly so good recipes are vital. Initially it would be safer to obtain some low fat recipes from a qualified pet nutritionist. We have some information about this in the home cooking section.
You will probably have to pay but once you have them, that's it. Don't try and cook for your dog without seeking advice because the meals need to be balanced. All home cooked meals need additives, the main ones being calcium and omega oils 3 and 6.
Another thing that might help is to feed smaller meals more frequently, maybe three/four meals a day