Thanks jjj111, you are very insightful, and helped to clarify some of my thoughts.
Monogomy wasn't a huge priority -- after all, we're two gay men in New York City.
But sexual compulsiveness and active addiction, no, I am not willing to live with that. I've been willing to live with a person who is attempting recovery, but I am facing the reality that his recovery isn't happening. He's trying, but he's slowly sinking deeper. And like you said, I need to protect myself.
How does one go about finding a therapist?