I'm a little behind you with a 16 (and a half) year old who is similar.
He is diagnosed with dyspraxia which is quite extreme in some ways and not in others. He potentially is on the AS too but we didn't go for a further diagnosis at the time.
He has been home educated since he was 8 as he didn't cope with school.
A few of his (also home educated) peers really seem to have found their way and are doing lots of exciting and motivated education, training and work experiences.
But he seems harder to help find his path. I have two older children who went to school and then university and seemed to know a little more how to go about that.
I was stressing about it just recently but have realised that he isnt his friends or his siblings and I think he will take a little longer to find where he wants to be.
So he has enrolled in an evening course that he will enjoy and has a few little projects in mind. And for the moment anyway I have decided to let that go on. But I get that your son is older.
I have always kind of felt that children are best to be studying or out working and if possible away from home by about 18/19 but I'm not sure that traditional path (if it even is a traditional path) is going to work for him. And of course that's much harder these days if you don't go away to University and stay in halls.
So as well as helping him, perhaps if its possible financially (that will be a challenge for us in the long term) can you let him try various things out without the pressure to really know where it will lead to?
I'm looking at work experiences and maybe pushing for a small part time job in time. And I'm kind of trusting he will find his path whatever that is, just maybe not as quickly as others.
I wish you and your son well.