I have been thinking two of you a lot. I haven't written much, because I find it difficult to come up with much encouraging to say, that would still be honest. So I decided to be blunt. Remember that this is only my experience and understanding and I certainly hope and pray everything goes as well as possible for your boy.
But only silver lining I'm able to really see is, that this may tip your son to be 'disabled enough' for many much needed services for also his adult life. If that is possible, my advice would also be to go for those now, that he is still a minor for a moment. It may feel, that if he would just try his best and do as he is supposed to do, he could make it on his own when he becomes adult. But what I know about his situation, that doesn't sound too likely to happen. Remember that disabilities do not add on each other, they multiply. If person has a cast on their leg they can still function quite well and even work in certain type of jobs. Same goes if they have a cast on their arm. But if both their leg and arm are on cast, they functioning will be very low and they will need help in even most basic functions.
And PTSD gets thrown around a lot to describe rather benign anxieties people experience that do not make much difference to their every day functioning, but when we are talking about clinical PTSD, it... well, simply put, it sucks. Co-morbid issues do not help. Nor does it help, that addiction is so common co-morbid issue, that it could almost be a symptom. Even less helpful is, that while some people find help from SSRIs, about all 'real' anxiolytic are both addicting and dulling. It tells a lot, that actually pot is one of the least addictive and dulling relaxants.
I have been watching my kid battle PTSD some years now, you have read some small titbits about his struggles from here. While he was not overall picture of stableness before he acquired PTSD, and unfortunately PTSD has destroyed lives of many who actually were, he did have a lot going for him. He also has goals and he really wants to win these obstacles and get better. He also isn't active addict now. And professionals have often commended him from having cognitive abilities and self-awareness that make his treatment and recovery easier. And we have looked for and provided best possible treatment for him (we have for example talked with most experienced experts on the matter not only in our country but couple others in hope for something new and revolutionising, but no, it is that same; intensive prolonged exposure therapy with experienced therapist with whom the patient has a good rapport with.) Still, if he wouldn't have very sheltered job, if he would be a student or try to work in some entry level job, he would be in disability right now. Can you imagine any entry level job, there you could spend a day sitting on couch and playing mobile games, if you had a bad day? Or spend the day working one-on-one with trainer on relaxation exercises, if you have slightly less bad day and can't perform your duties?
Unfortunately I also don't believe this awful experience would teach him to avoid jail. Trauma doesn't work that way. Unfortunately person who experiences trauma in incarnation (and because of the situation it tends to be very damaging type of trauma) is still more likely to learn to have a panic attach when they smell a triggering smell or see a person who remind their abuser than to learn that it is a bad idea to break a law and end up to jail. In fact the trauma makes it more likely a person to get into trouble.
I know this was very gloomy. And in reality many people recover from PTSD really well, and many others learn to live with it. And your kid is in treatment and he has every chance to recover and do well. But it will unlikely be easy, quick or stable road. Best thing I can recommend is to find every possible service he could get. It is very possible he will need many of them.
I really pray you will be luckier with all of it than what my kid seems to be with his PTSD and I'm sorry I wrote such a depressing message. But whatever will come, will come and I just hope that you will not end up expecting something that is not likely or even possible, but rather prepare for the worst (and of course, we all hope for the best for you and your kid.)