I'll be anxious to see what the others have to say about this, but I'm very wary of having you state -- YET AGAIN -- what your boundary is ("I need you to send OW a no-contact letter.") Ordinarily, I am a big proponent of "A boundary constantly re-stated is a boundary weakened." My only hesitatation on that in your situation is that I'm NOT sure that your husband has really HEARD you thus far that this is a dealbreaker for you, so I dunno.
I do think you are still confusing one thing, however: this is neither a "demand" NOR a "request." It is a BOUNDARY -- which is simply a "You can do whatever you want; THIS, however, is what I need in a marriage where there has already been infidelity."
Not sure if I had already shared this with you or not, but this -- from a friend of mine -- was the single best way I've ever seen the concept of "boundaries" explained:
Think about boundaries like this:
Boundaries are not about controlling the other person, because boundaries are about drawing "circles" around *you* and determining what you will and won't allow inside that circle.
Your WxH can do whatever he wants OUTSIDE that circle. You are not telling him what to do.
But you will only let into that circle people who treat you with respect.
He's free to go on treating you with disrespect, but you won't know about it because he'll be outside your circle. He's free to go on and draw his own boundaries of no expectations and no responsibilities, outside your circle.
He can do WHATEVER he wants. He's a free person, free to make WHATEVER choices he wants.
BUT SO ARE YOU, and you are free to choose who to allow within your circle.
That's all. Not about trying to control him at all. Tell him he's totally free. He has the WHOLE WORLD, outside your circle, to go and do whatever he wants.
If he's saying you have to let him into your circle no matter what, then THAT is about HIM controlling YOU.
