That really sucks, but you have at least tried a lot already. You many have some dysbiosis going on in the guts, but in the meanwhile - how about some ideas:
1. Try a moisturizer with Vitamin E + B3 at the bare minimum, other ingredients should be fine like Vit. C, Aloe, Green Tea, and other oils to keep the skin barrier from losing moisture.
2. Eat more traditionally cultured and fermented foods, not commercially cultured foods.