I think there are a lot of good suggestions here. The kids are controlling the relationship--they have been given too much power. It sounds like your H is letting his kids ruin his marriage. I think it may be easier for him to hear some of this from a professional rather than you. Can the two of you find a good family therapist and go together to see him/her? And maybe some sessions with the kids too? Maybe especially some sessions for just him with his kids?