I had a very bad skin condition last year and saw two consultants one privately and one for the NHS.
Skin is a tough one, no pun intended, what seems to work one day doesn't work another and doctors tend to prescribe steroids when often its a process of elimination and like you say using therapies that work for you.
I was told by both consultants it was really serious, and seemed to disbelieve me when I said it was getting better without steroids, its a bit like the low carb diet, if it doesn't conform to their knowledge its doesn't work. Perhaps they are not ignoring you they are just out of ideas. To see a private consultant was about £250 and she was far more through than the NHS, she wrote me a private prescription which I used about half of, but I thought she listened.
I found forums really helpful, for my skin problem, lots of different ideas, some of them a bit quacky, I had a cupboard of lotions and potions and just worked though them.
Its tough with children, you have to find what works for you and your child can tolerate. Raised blood sugars are a well known side effect of steroids, he is off the steroids so that will resolve. If you are worried about what he is eating start a food dairy and see if anything he is eating is making his skin worse, but increase his calories, and see if there is a pattern.