I am so sorry for your pain and confusion, RC. When the Difficult Child is a minor that has to be so much harder. My son's truly bottom behavior didn't escalate (at least on the surface) until he was between 19 and 20.
What else can you do, other than what you have already done? Sometimes we have to completely let them go.
We're here for you on these forums. I hope you will read and reread here. There is a lot of good thinking and recovery work being done on this site.
Warm hugs. Please keep posting. We get it and we care.