You are in the UK, If you go and speak to your G.P he can refer you to talking therapies, you may be on the waiting list for a short time but its free and will inshAllah help for you to talk things through with a professional. I know things are tough right now but no situation ever remains the same. You work a lot of hours and seems your issues are mainly surrounding finances, you could try and speak to someone about managing your finances better so maybe you won't have to work as much. You say you can't go back to studies, how about an apprenticeship? At least you will get paid for on the job training but be in a better financial position once thats done with. There are quite a few options and I hope you find something best suited for you.
Seems you have many good qualities, you are a dutiful son trying to look after and help out your father now that he is not well enough to work and a married man managing many responsibilties. I am sure your family really appreciates all you are doing for them and would be really proud of you.
You are going through this because believe it or not you are much stronger than you think and able to handle it. Hoping and praying things become easier for you.
لَا يُكَلِّفُ اللَّهُ نَفْسًا إِلَّا وُسْعَهَا
“Allah does not burden a soul beyond that it can bear…” [Qur’an, 2:286].