Have you spoken to your bank? You seem to be just accepting the charges when often if you talk to them and explain the circumstances they can suggest ways of helping - eg freezing interest, stopping charges, even just switching you to an account with lower or no overdraft charges. Or even a personal loan. An overdraft is one of the most expensive and hardest types of debt to manage.
Secondly if you're in England/Wales I recommend speaking to mind. They're very good ok advising on dealing with the financial impact of being mentally ill.
Martin Lewis is also campaigning and working on getting people who are mentally ill treated better by financial concerns. Plus if you go on mse site there's loads of advice. From basic budgeting and money saving to more specific advice relating to your particular circumstances. It does sound like you went straight to using savings rather than reducing outgoings.
You could even post a new thread here outlining income and outgoings and asking for suggestions for money saving. There's lots of us on mn on tight budgets that know ways to save.
He may also find discounts/deals on his hobby item - though I agree NEEDS come before WANTS. Shelter, food, clothes, utility bills all take priority.
Are you SURE you're getting all you're eligible for? Have you checked on benefits calculators? Spoken to welfare advisors? Even hcps can put you in touch with advisors on this. My Cmht has an in residence advisor on such matters.
It's unfortunately common for claims based on mental illness to be rejected initially, but many are overturned on appeal. I had to do this.
"I want him to return to work, even just a day or two a week but he feels like he can’t. We are receiving all benefits we are entitled to. Treatment hasn’t helped. At all."
So ESA, pip, housing benefit, council tax rebate or equivalents?
What treatment has he had/tried and over what time scale? Has he seen a psychiatrist? Does he have a proper dx? Or has he ONLY seen GP and psychologist?
"I’m not being paid in September due to time off for caring responsibilities, unfortunately I’m not entitled it so can’t argue for it."
"If he can keep going to/ attending his hobby then he should be able to go back to work" lovely bit of mentally ill shaming there!
Jesus! Believitornot - So basically he should "just pull himself together"? You wouldn't be saying similar if it were a physical illness/injury!
SO MANY myths and misunderstanding on this thread about mental illness generally and depression in particular.
What work was he doing? What are his qualifications/experience? We might be able to suggest something that suits?