I think the coconut cowash works really good it doesn't have any sulfates or silicones and it helps prevent buildup in my hair between shampoos.
And steamers are different from just applying heat when deep conditioning because it helps penetrate the hair shaft with water instead of dry heat. I know deep conditioners didn't do much for my hair when it was relaxed nor when I was natural with or without heat. It wasn't until I started getting steam treatments that I actually saw a difference with moisture in my hair. I mean its worth a shot seeing as how nothing else has seemed to work and salons typically charge between $20-$40 to get it done.
I hope you find something that works because i know first hand how horrible dry hair can be. I was at my wits end quite a few times dealing with how brittle and rough my hair was that I too thought only going back to a relaxer would help me manage my hair and not leave it so dry, but I'm glad I didn't.
Don't give up though I'm sure your solution is out there