unplainjane:

It seems to me you gave him a boundary - therapy - and that he has reneged on that.  Therefore you have every right to ask him to leave your space.  You do know, of course, that if he harms himself  you hold no responsbility to it.  He has family and they can be there for him.  I beg you not to give up your future for someone who is unwilling to do the modicum necessary, which is to stay in therapy.

I think there is a co-dependency thread buried here.  If you set boundaries that are disrespected, yet do not hold him accountable, you are enabling him.

I was terrible with that.  My XDSO crawled back to me in last March and I told him he could come back as long as he was actively in therapy.  He did not go to therapy at all, and I was so happy just to have him back that I walked on eggshells for 6 months rather than hold him accountable.  In the seventh month he left me, in the 8th in contacted and went to therapy exactly 7 sessions and quit.  He has not been back to therapy since October.  He is more erractic than ever and I am now relieved to have no contact.  I miss the old him desperately, but now know that that version of him is long gone.  Even with therapy, too much damage has been done between us and I am trying sadly trying to move forward.  Mine also spoke of suicide.  

Only he can help himself.  only he can save himself.  Only you can protect yourself

strength to you.