There are reasons that people won't have anything to do with him. Do you have visions of rescuing him?

What sort of relationship do you have with him now? I am wondering why marriage needs to be a next step. What about insisting that he prove himself, over an extended period of time, in a relationship where there are boundaries that you strictly maintain?

Even if this is true, it doesn't mean that he has to do nothing. How useful is he being to you right now? How constructively does he spend his waking time?

There is a huge difference between "I have forgiven him." and "I want to entrust my life to him again." It is quite possible, and quite logical, to forgive someone but to recognize that the person should not be re-entrusted with what he proved himself to be so unworthy of.

I urge you to discuss this major, life-changing decision with a therapist--at length--if you are not already doing so.