I know that "kicked in the stomach" feeling. It's awfully painful and I'm sorry for your pain. I will keep you and your son in my prayers.
Two positives that I see:
1. It sounds like your son has experienced what it is like to be sober before he relapsed and he can always draw on that memory of sanity and serenity if he chooses.
2. Your instincts are very good. They may not have led you to a place of your choosing but they led you to the truth.
PS - Love your signature, Queen!