Similar story for my DD - high functioning autism, also on meds due to anxiety / anger. School refused from the beginning of year 10 due to bullying then attended online school for year 11 but only passed her maths and English GCSEs due to missing a lot of her education (combined with exam stress).
With only 2 GCSEs this restricted her options quite a bit (ie she couldn't go down the A level route but I don't think that would have suited her anyway as although she's very bright she struggles with exams). She ideally wanted to do an apprenticeship as she finds it difficult being in a formal education setting / around people her own age and although she applied for a few she wasn't offered any interviews.
In the end she ended up doing a level 2 vocational course at college in a subject she loves (animal care). She really enjoyed the course which was part time at college and part time on a work placement but unfortunately she also experienced some bullying at college in her first year although she passed her course with flying colors.
She has now changed to a new college to continue down the vocational / animal care path and absolutely loves it. As she's also doing a work placement this has given her some real life work experience to add to her cv and has also helped to develop her confidence too.
We have found college very different to school, the staff have been much more helpful, there's free counseling and mentoring available and things are just more relaxed generally. The students seem to be treated with more respect by teachers and are allowed to express themselves as individuals (eg hairstyles and clothes they feel comfortable in which has helped sensory wise too).
How is your DS expected to do in his exams? If he's very academic then the A level route would mean he can choose a range of subjects so he could do those (keeping his options open for a while longer) then choose a speciality later for a degree if he wanted to.
If you think he would be more suited to a vocational course he'd need to pick something he at least has some interest in, there are a lot of subjects to choose from but unfortunately you can only pick one. These are mainly assignment and practical based so have been much less pressure for my DD than her GCSEs and
she has coped much better generally with less stress all round (we have noticed a big difference at home too).
Does your DS have any hobbies / special interests?
Have a look at the national careers service website, there are questionnaires he can do which will come up with some suggestions of careers he could be good at etc :
nationalcareers.service.gov.uk/