It's sad that he is seemingly wasting his life at the moment but he is the only one who can live it. I think with a child at his age who refuses any help, you kind of have to step back and hope for the best (rather than expect/wait for the worst, the phone call). It does not sound like there is much communication between you so, as you say, you can't really know what's going on. I was not doing so great at his age either but I will be 60 this year and like who I have become and my life. Put some hope in the future and in his ability to learn to navigate his life in a way that works for him.