I'm a fellow sufferer. Nightmare, isn't it? For me my scalp always has to come before my hair when making choices, and there are so many things it won't tolerate.
The best thing I've found is vegetable glycerine! It's amazing stuff. It hasn't cured me, but has made things much more manageable.
I don't use a sulfate shampoo, and in fact I don't shampoo daily, but I do water wash daily, and scrub my scalp. I shampoo approx weekly (or sometimes twice weekly, depending on how things go) with a sulfate-free shampoo. I actually went without shampoo for 4 months once, which didn't make my scalp any worse (or indeed better).
Based in the UK. 2-something (2b?) hair. Very porous, fine and brittle/fragile
Hair loves: Drip drying, glycerine, shea butter, oils
Hair hates: Plopping, any kind of gel, most conditioners (scalp issues).