I'm picking up a lot of defensiveness on his part? It is not an easy task for anyone to adapt to the outside world, which makes little sense to anyone at times. Yet he seems to regard everyone who does as someone worthy of scorn?
The large amount of smoking might be a stress reducer for him and I am sure he can use one if his standards are so narrow and his outside abilities so few. He doesn't see a way past these barriers so he scorns the task.
It doesn't mean he can't do it, though. It just means it is not nearly as simple as it might look from the outside.
And you should also consider your needs. You need to launch your child into the adult world; where people are self-supporting. You need to see him happier and more productive than he is now. You need to see him make his way in the world.
I sense you are worried about him. I don't blame you for worrying. But I can also say, from my side, that he worries about this too. That he doesn't see a way out. There is incredible stress here and he is coping as best he can.
There is a creative solution that will make both of you happy. But it will not -- NOT -- be any kind of conventional path. He has already been looking at those and it is part of his despair and stress. But the world has never been more welcome to people who work at home on computers, and this often falls into an Aspie skill set. Not just computer coding, but managing social media, creating consumable content like writing or video, doing chat and email tech support; there are many ways now.
He needs a challenge. Perhaps this can be one