Has Ziggy ever been allergy tested? Living on peas and beans for the rest of his life can't be too healthy. I can see why you are concerned.
I know people with allergic dogs who have improved a lot after allergy testing and allergy shots if necessary.
BTW, has you vet ever suggested adding fatty acids? Lady has allergies and my vet suggested it years ago and it made a huge difference.
Fatty Acids for Allergies & Dry Skin in Dogs