This is a hard situation. He's got some major issues that he has not addressed. Stacking on the responsibility of a child/family only serves to add pressure and make it worse.

While it makes sense that you want everyone to be a family again, the important key is that HE wants to make it a family again. He has to want it that. He also has to want to work on himself. Owning your own issues is hard. I had a tough time with it.

I'm not one for ultimatums, but I did give one to someone I loved, in the name of setting boundaries. Maybe this will be helpful. We had just started dating, and it soon became clear that she wasn't handling her mental health issues very well. I had just gotten out of my abusive marriage, so I wasn't about to be very accepting of this, especially within the context of a new relationship.

I told her that she had a choice to make: You can neglect your own mental health, and do it away from me, OR you can take ownership of your mental health, and I will be happy to help you.

She accepted responsibility, and I helped, as promised. She stayed on track. We've been together 18 years.

There is hope. Maybe you can offer to help him, so long as he is willing to help himself. That doesn't mean that he moves back in, because that will make it easy for him to slip back into the old, comfortable ways. It means that he takes charge of his own mental health, and then makes himself worthy and capable of caring for a family.

Best of luck.