Hi, welcome to the site.
If he's Aspie, etc, is he thinking of this himself or is he being led by others? I know my Aspie older son would never do anything like this, but another Aspie young friend is constantly in trouble with the police because he tries to buy popularity with the 'cool' kids by doing what they want him to do. His last big brush with the law was carrying eggs around for the local thugs on Halloween (which is not popular here in Australia - local bullies have hijacked it). The cops searched his bag and found nun-chuks in it (they're an illegal weapon for ANYONE in Australia, and he was under-age AND carrying an illegal weapon). He had put the nun-chuks in his bag as a favour to a 'friend' who had used them earlier to beat up another kid. "Here, you mind these so when I get searched they won't find them on me."
How stupid can you get? This boy's parents are good people, totally at a loss as to what to do to get through to their son.
Back to your son and your problem - yes, he needs to be assessed and seen by an expert. You also need to talk to someone (as part of the team) to put strategies in place to ensure he does nothing more in this vein. My concern is, that if all you do for now is REact, instead of being PROactive, he will turn it into a game - "beat Mum's latest obstacle to my joy-riding."
Some practical suggestions for now - get a kill switch installed in your car. We had one in our car (from a previous owner) that we didn't even know was there until husband accidentally kicked it on one day and we had to get our car jump-started until I took it to an auto-electrician. It took the experts half an hour to find the switch, so a well-hidden, secret kill switch in your car (don't tell him or mention it in his hearing) will keep him puzzled. You kick the switch when you get out, kick it back again when you get in to drive. Ours was a quarter-inch toggle switch on the floor in the corner, away from the steering column. Get it put where you can reach it discreetly, but where it won't be found by fumbling fingers (ie don't put it anywhere near the steering column or where someone trying to adjust the seat could find it). Base of gear shift, if you have a floor shift, or base of handbrake is a possibility.
Use the kill switch WITH a club lock. Belts and braces. Let him think you're relying on the club alone.
Get the house wired for alarms. Get movement sensors installed outside his windows. A remote movement sensor leading to an alarm in your room would slow him down some. If you also have consequences in place for him trying to break curfew, then hopefully he will learn to not break the rules because he won't know what you're up to.
Keep him guessing, whatever you do. Don't let him know what you have or where it is.
Instal nanny cams. Put one in the car. Another in his room. Another outside his room, using infra-red. Put one anywhere you think you need coverage and include infra-red if you can. Be as discreet as possible and check the films behind locked doors in your room. If possible get them solar-powered, or battery powered. Mains power can be cut. You need battery back-up, at least.
ALWAYS - keep a logbook for your car, write down mileage. We have to do that by law with our young adult drivers, plus husband keeps a log book to help us with car maintenance. It's not difficult. But it's very hard to hide if somehow a mysterious number of miles has been added to the meter overnight.
And yes, drug-test him randomly and regularly. Bring back chores, accountability, keep him busy and tired. Get him a volunteer job somewhere, maybe at an old folks home. Make sure he's supervised. Never let him sleep in - always get him up and working, even if it's study for school. Even on weekends - never let him sleep in. I use a water squirt bottle up the pyjama leg to get any sleepers out of bed in a hurry. But you need a reason to get him up - enrol him in a sporting activity such as self-defence classes, sport classes, whatever you can that will give him a place to be and something physical to do. NEVER let him off it unless he has a broken leg, and even then he can go and watch.
Basically, keep him tired enough so he'll go to bed earlier and not want to get up in the middle of the night, especially if he knows you will be dragging him out of bed at 7 am (that's a sleep-in on the weekend).
You need expert help. Not only talk to the health professionals and counsellors, but go talk to security firms who specialise in nanny cams etc and pick their brains. And when he's no longer under your roof - everything you're learning and acquiring will set you up for a career as a private detective.
Be inventive, be suspicious but also be good-humoured. Keep him guessing, keep him active and good luck.
I'm one MEAN Mama!
Marg