What does he enjoy?
What would be his 'dream' way to spend his time?
What are the things he really hates?
What are the things that cause the most stress?
Get him to really think about those and emphasise that, especially the last two, aren't necessarily the same thing.
They're questions we've been asking autistic DD as she comes up on college applications and starts looking at careers. It was interesting to see how differently she saw some things and that, in fact, some of the things she enjoys most would likely also leave her exhausted taken in a 'career' direction, whereas things she hates, she can cope with day to day fine. 'Boring' can be an asset here.
(FWIW - It also became very quickly clear why we're seeing such a surge in people not able to find work that suits. We're losing hundreds of roles that people with these issues would have slotted into just fine. DD, for example, would have been an excellent 'old-style' librarian - cracking memory, loves books, polite, peaceful and just a little quirky. She'd be perfectly happy spending all day cataloguing, shelving, tidying, finding things, chatting, making suggestions and from time-to-time, deep-diving a topic with someone and it is her 'dream job' - but the role is dying off at speed, certainly as a paid job that can support someone, and the way the GCSE English exams are structured is so NT biased that despite a vocab and reading score off the charts, and predicted 8-9 in other essay based subjects, there's no way she'll be able to get anywhere near the grades at GCSE and A-Level in the subject to open the field anyway.)
In the short-term, yes, he absolutely should claim. He's tried, it's making him ill, and he needs to step back and let everything settle down again.
But it needs to be framed as a window to reset and make plans, and not as 'here, do nothing' as that leaves him very vulnerable moving forward.