I'm normally one to say to parents: Butt out.
However, in this case, you need to act on his behalf. He's clearly quite ill, and probably also feeling a mixture of shame, embarassment, anger and helplessness in the face of what he sees as failure. Sounds like he's got his head in the sand and hoping it will all magically go away. It won't and you both need to take swift action.
The behaviours you describe are textbook symptoms of a bout of quite sever depression. ADs will help, but he also needs to make lifestyle changes: some vigorous exercise everyday, sleep hygiene, and eating a sustaining mix of protein and vegetables. I also suggest to students in this situation that if they are musicians, or paint or draw, or have some sort of creative hobby or sport, which takes them 'out of themselves' they should try to revive that interest.
These simple things are recommended by our student counselling service as necessary self-help, alongside medical and/or counselling intervention. A big emphasis on gradually introducing self-care and resilience, and managing one's illness. It's tough, but I've een it work with my students over the years.
The university, and his individual tutors, can talk to you if your DS makes it clear that you have his permission. Probably an email, or written note from him, to his Personal Tutor and Course Director. Then you can go from there.
I think you should explore the possibility of him taking a year's leave of absence (intercalation or interruption some places call it), for him to get better. If he had a cancer, that's what we'd advise. An intense experience of a mental health problem is just the same.
I can't really advise on the funding aspect. BUt you do need to stop the clock, as it were, and in this situation, the university will work with you, I would hope.
We don't like to see students fail: for their own sakes and also it's such a waste of precious resource of time & energy by both student & staff. It's a huge investment by everyone (and no, the £9k doesn't cover what it really costs). So decent universities and staff within them will really work hard to assist & support.
The difficult bit is getting him into action. Good luck to you both!