Draylon the other threads filled up.
(OP sorry for slightly derailing to respond to Draylon who is in my area)
First, people do 'restart' 6th form as in after not succeeding in first year, restart on a different 2 year course. (I know this as I asked when we looked round places in case DD did A levels and couldn't cope). So if he blows this year in terms of results he can restart (elsewhere with new kids?) a different set of courses elsewhere.
I expect you did all this when you were looking for Plan B and Plan C before, but does he have any interests / skills that might direct him towards a career or a relevant BTEC?
DD has gone for a mixed BTEC / AS route at Brock (who do a wider range of BTECs than BP and a full range of A level too). But we found finding a BTEC hard as she also has no real idea of what she might want to do career wise. We found the Brock one in the end and it ties in to her outside interests and general skills.
You know the open evenings are on again? BP this week, PS soon, and Brock next week and the week after. Eastleigh no doubt too and probably Sparsholt. Any point in going and looking around them with your DS?
I suspect but don't know that it is too late to swap courses now (especially as he doesn't have an urgent desire for something else), so I would think maybe better to pursue the AS unless he is chucked out / he comes up with an alternative plan for the future. At least he is going in to college for lessons, even if not staying there for frees. If he just drops out he may sink into doing nothing at all (and child benefit will stop I think, so if not earning by dropping out he'll cost you money).
I expect you just want to give him a good shake!
ps Are you sure he is capable of arranging his own self-study? It's not that he can't but doesn't want to admit it? (I'm sitting with DD every evening and agreeing what she will do in the next day's frees.)