As a parent, it is very difficult to stop doing things to help. But you must think of this as help that harms. Anything you do to help him out of problem situations actually can harm in his recovery. I can see that you have started doing some good things to help him such as cutting him off financially, and not bailing him out of jail. These will help in the long run.
It is important to look at the big picture for him. The future. If you can help him feel some pain it will help him stay motivated to be clean. The outcomes of the disease of addiction are insanity, institutionalization, death, or recovery. Since the first three outcomes are unacceptable to a parent, the last is the option. In order to help him stay motivated to be clean, it will be important for him to choose that path himself. People choose the clean and sober path because it becomes too hard to keep using drugs/alcohol. This means he must experience pain in some way, either emotionally, financially, mentally, legally, work, family, etc.
As for you, it will be vital for you to have a good support system to assist you with this. The Al Anon program can help you for free, or you can get some help through a professional counselor. The Al Anon program has meetings for family members or loved ones who have an addicted person in their lives. This program teaches you how to get healthier by focusing on your self rather than the addicted person. You also have an option and recommendation to obtain a sponsor. This is someone whom you can call for assistance, to talk, cry to, and who has been where you are, and knows how to help you deal with what is going on. I am including the website for more information, and to find a meeting in your area. http://www.al-anon.alateen.org
I hope this helps. Be selfish for you and you will get heather, and help your son as well. Please let me know if you have other questions. Thanks, Gina