Good for you for going to Alanon. Good for you for recognizing that you need the perspective of others to help you distinguish between supporting and enabling.
I too have a young adult son who is an active drug/alcohol user.
You'll learn a lot at Alanon. Also come here. Also, if you are a reader, there are lots of good books out there. I recommend "Addict in the Family" by Beverly Conyers. You can find it at the Hazelden site.
Keep coming back!!