Sorry to hear your story. I have a 20 year old son also. He no longer is in our home and I miss him but I'm glad he's gone. He's in sober living in Florida and has a job and we do help financially but he is now taking more responsibility for himself. I do not believe he will ever be allowed to live with us again.
You seriously need to detach from your son or he will be doing the exact same thing 20 years from now. I met an older couple that had a 34 year old alcoholic son living in their home. The were spending all their money paying for his legal troubles. I knew I did not want to end up like those people. Tough love was hard for us and it took us almost five years to enforce it but we finally have some results. No one should treat you like that. Drugs or no drugs. Totally unacceptable. Good luck!