
Have you tried Sudocrem? Its the only cream/medication I use on skin irritation now, and then a bit of aloe vera gel when it has healed. Might be worth giving doreen paige grooming a ring as they do a brilliant range of shampoos for problem skin.
Diet wise....make sure the chicken is balanced with meat:bone. Minced chicken wings or carcasses are ideal, and most butchers can provide this. Ratio wise it really does depend on the dog. You need to make sure the diet varied enough including tripe offal and other muscle meat. Id be tempted to ditch the rice and cut out the grains all together. Might be worth reading one of Dr Ian Billinghursts books to give you a general idea, although I think he is a bit excessive with supplements etc it will give you a rough idea.
Sorry if thats a bit babbled. Long day!
HTH