I think your partner should stop talking about this other woman as a "friend" and be more transparent with the fact that this is a woman he desires or desireD outside the friendship zone.   If you want monogamy...don't settle for less. Sending nude pics of oneself to another person can be considered cheating...it depends on your boundaries. Make these clear.   Alcoholism is serious and one part of it is dealing with accountability. Not lying. He might have stopped the alcohol but has he stopped lying to himself or you? Don't fool yourself into thinking alcoholism is just about the bottle. There are web of lies and difficulty facing the truth. I think if you two want to stay together, serious boundaries need to be set and he needs to break up with his "friend". No texting, no contact. If he can't accept this, I would say: leave. Be honest with your own boundaries and encourage him to be extremely accountable and transparent.