I think you are doing the right thing. I cannot imagine how hard it is as I have no children. You asked for encouragement.. you got it.
I wish someone had handled my XABF the way you are handling your son. If that had happened when he was young maybe he would not be an addict of 40 years?
We can do nothing and nothing changes. We can do something and nothing may change but we have increased the odds in our favor.