i no you said that your tried tea tree, but have you tried mixing tea tree with argan oil? or jojoba? if that really doesnt work, there are herbs that you can get that can help with scalp problems: marshmallow root is wonderful, to make it better make a rinse combining stinging nettle as well, ive read that stinging nettle is great for scalp conditions. use that and marshmallow root as a final rinse and see how you go

my hair: 3b, high porosity, high density and coarse hair (i think i finally figured that all out)
my hair loves conditioner only styling!
Oils and my own procuts are my hairs best friend
my hair goal length is bra strap length when curly.