I can totally relate and I feel for you. My DS did not get into that much trouble but formt he day he turned 18 my life has been in utter turmoil.
What I have done:
Not home by curfew I lock the dead bolt. You know the rules an dif you can't follow them than you don't get back in.
I will not cover for him. If he gets in trouble it is his problem. When school would call, I was honest sorry, I dont' know where he is and nope not a legal excuse. Whe I was told he was in danger of not graduating and they shared the option of summer school or GED I reminded the school that they forgot that he has the option of returning as a super senior...Whatever the pricipal said to him seemed to do the trick, he is in school everyday as he is supposed to be...only missed 13 days total.
My insurance will not let me take him off since he lives in the house. I simply do not let him use the car. I take my keys everywhere with me.
Cell phone, he has one now, but I had it turned off when he was giving me too much trouble. Just went to the verizon website clicked a few butotns and had it shut off while I continued to pay throught the end of the contract. He found ways to communicate without it.
If I were you I would stress that he does not have an open door policy with you. If he leaves this time, while you love him and want to support him emotionally you will not be able to do anything else for him.
Adult choices and decisions equals adult consequenses for the better or the worse.
I would throw him under the bus so to speak, with the court system though. Only because in the end he wil have done way less damage to himself by dealing with it now.
Some kids do stupid, irresponsible things that are self destructive. It is our job to protect them when we can, and guide them when they will let us. It is unfortuantely our job to watch them fall flat on their faces and hopefully to be able to help piece it back together when they have learned something from the fall.

I know how hard this is, but you have to play hard back.