I think this is an excellent suggestion. A healthy, well-functioning marriage can meet a lot of your attachment needs. There are far fewer limitations than in the therapeutic relationship, and you get the added benefit of a self-esteem boost from seeing that you're capable of meeting your partner's needs too.

I think sometimes it can be a lot easier to focus on getting more of something healthy and productive (stronger relationship with H) than to try to forcibly stop yourself from wanting something less healthy or productive (more contact with ex-MC). If you direct your attention elsewhere, eventually the urge toward the unhealthy thing will subside. Or at least that has been my experience with relationships that I know I need to leave alone.