It does seem like you have tried everything.
But I have some suggestons that might make a difference.
When I scrunch hair like yours, I put LOTS of product on it and then I don't dry it all the way. I use seerum and cremes - often together- Anything that is made to control frizz without getting stiff.
I don't touch it untill it is completely dry.
I have found that using a ceramic flat iron works so much better than any other kind.
I use lots of moisturizing conditioner.
I hope these tips offer some help.