You make him sound pretty sweet despite the things you are saying and he has always been like this so I would hold off on the big life decisions until you have seen a doctor and got checked for thyroid, iron, all that stuff, and maybe got some counselling.

Making big life decisions when feeling very down never worked out for me. When life decisions are thrust on me I always muddle through, but not so much when I try to decide stuff when down. You sound desperately sad, maybe you could ask him for help? If you cannot face food so much some malted drinks might be in order, your doctor can probably help. What does work for me is plans. I make plans for every possible scenario. Which I then forget, but I like to do it.

It sounds as though he isnt a bad guy, just not at all what you expected from a partner?

He may have an underlying issue like ADHD which can be treated even in adults.

My friends brother was like this and he grew the hell up in his forties or maybe he just got work to avoid being responsible for home duties, history doesnt say.

I would take over the car payments yourself and give him his allowance minus the payment. No more joint debts until he has been grown up a long time.

If it is a hobby business it is always possible to start small and go up. He has already started small. He could jump into a job for a while to save up for it, also. Or in his case to progressively waste his pay cheque to buy the stuff he wants, doesnt sound like he is really a saving kind of guy.

It may be possible to save this relationship, maybe by not always being the adult. Ask for his support about feeling sad, talk to him about scaling back your work and making friends maybe, kind of place him the situation of you being the needy one, and demand cuddles? You are taking the responsibility " I must have done something wrong" about his behaviour. Which is fine if you want that but maybe things have just got too much. Maybe it is your turn, and now you have to seek support from someone who isnt used to that role :(

I think if you are going to support him either way you might as well as have him with you, but get counselling. If you arent willing to let go of the idea of an adult partner you are going to have big job on your hands. He just sounds so ADHD.