I think that it's important to learn that this challenge is a lack in him and really had nothing to do with your being worth an honest commitment. It's also clear he doesn't want to let go of his addiction problem which is why his therapist stopped working with him and realized it was a waste of time.

It's hard when you love someone and want to figure out how to make the relationship work and the partner can't or doesn't want to change their problem or addictive behavior. Don't beat yourself up, you are hurt and disappointed enough, you need to get help to heal now instead.