I think maybe it would help if you imposed a waiting period of 24 hours between when he asks and when you say yes or no. Time that he can not call and ask for more, or pester you about anything. If he does, it means the answer is no. I suggest the waiting time because it gets you out of that emotional cycle of being at the end of the chain that he yanks.
You also need to reframe your thinking. He isn't in this situation because you called the cops. He is in this situation because he was taking drugs and acting irrationally, which made it necessary for you to call the cops. He wasn't sitting quietly and reading the Bible when you suddenly decided to call the police on him. I feel quite sure of that!! He was doing something that was unacceptable and dangerous, so you felt the need to call the police. Good for you!!
What are you thinking of to put a vehicle in the hands of a drug addict? I don't care how old he is. He doesn't sound capable of paying for insurance. That vehicle is a very heavy lethal weapon aimed a groups of innocent civilians every single time he operates it. I would leave it broken on the side of a road before I put my drug using or alcoholic child in it. I wouldn't want my child to die, much less to hit someone else.
Many years ago, my brother and 2 close family friends were almost killed by a very drunk and stoned college kid. My brother almost died. He himself was not drinking that night. He was a binge drinker who later became a raging alcoholic. He has seen both sides of impaired driving and he regularly begs parents to refuse to let their children who are not in recovery drive. Ever. Let your son walk. When he pesters you about his vehicle, picture the family of a preacher with four or five kids all mangled in the wreckage after your son plowed into them.
The 24 hour waiting period between your son asking you and you answering his request is a way for you to figure out if you really want to give him what he is asking for. Is it something that he needs or wants? Something that he can use to hurt someone else, like a vehicle? Or food or a coat? If it is food or a coat, I would probably say no because he can find shelters and churches that give these things away. He is not too good to make his poor mother support him, he is not too good to go and get them from a church. Maybe having you expect him to support himself, or figure out how to live without supporting himself and without you working your poor fingers to the bone when your children should be helping you, would make him want to get clean.
Dual diagnosis does help, when they are ready for help. It addresses both the substance abuse and the mental health portions of the problem. You have to make their lives hard enough that they want to get clean before they will accept recovery though.
Remember that YOU are a factor in all of this. Support from NarAnon/AlAnon helps, as does private therapy and posting here. Reading books like Codependent No More also help. Sometimes you give your kid a coat because it is winter and your Mommy Heart just can't stand the thought of him being out in the cold. That is okay, as long as you are aware of why you are doing it. It is okay to do those things for YOU.
It is also okay to tell him that he cannot speak to you in a rude or abusive manner or you will hang up. Then to go ahead and hang up each time he does that. And to not give him whatever he is demanding/asking for when he is rude/abusive. If he cannot speak to you in a polite way, he shouldn't get what he wants. Trust me, he can learn this, especially if you keep most of your contact to over the phone. Don't give him what he asks for just because he is polite, he should still hear no and have to be polite. Manners are not a magic button that grants wishes. Bad manners certainly should be a magic button that denies them, except when the badly mannered person is in your face and would hurt you if you denied them.
Above all, I know that you can't take all of the advice given to you by everyone here. Take the advice that works for you now. No one will be offended if you don't follow their advice when it is given. We all know that we are on this journey at our own pace, and that what works for us isn't what is right for anyone else. Don't be afraid that anyone here would ever judge you. We are not about that. I tend to come across pretty strong, and I can be blunt, but I would never get upset if you did what was right for you or what you felt was right for you at the time. This truly is a soft place for parents. I have been here a very long time and through some horrific things that I didn't think any other parent could understand. This group of parents understands. So even if you go away for a while or a long while, know we are here and you are always welcome. No matter how old your son is.
