This really rings bells on so many levels, your son is the same age as mine, and has his sleep pattern all messed up. It isn’t your responsibility, and this is what alarm clocks are for. If you want to do something, then maybe agree with him to leave his mobile on and closeby and you ring him once each morning, but this really is down to him. If he can’t do it at the start of a job he’s going to really struggle when the mornings are dark and cold in a couple of months time, so I wouldn’t feel too guilty.
I think its a really painful process that we go through, from when we first find out about our children’s problems and thinking that we can help them, to the gradual realization that there isn’t a lot that we can do other than tell them they are loved and provide support when they are ready to make changes. Someone on here called it ‘a slow death’ and its like that, a grieving process, in letting go of all of the normal things that you want for your child, to just hoping they survive their own behavour.