Well, damn, I hate to say this but have to call it as it is.
You have gotten yourself attached (somewhat) to someone with deep emotional problems. There's going to be a huge tendency for him to construct a dependent relationship with people - YOU in this case! You will become his support system, nurse, ad hoc psychologist etc.
It will likely be a turbulent, stressful affair. You are going to have little freedom to make choices in your own life that take you in the direction you want to go.
If there is ANY possibility of doing this - and ASAP - I suggest you extricate yourself from this situation. Explain to him that as much as you DO care about him, NO relationship can grow and blossom unless the people in it are healthy. Go and work on your own health and let's talk in a year !
I know this seems cruel. It FEELS cruel. But having seen SO MUCH of this I can't see any better alternative.