Good job Rain. I think it was important that he heard one thing: You recognize that he would need to feel safe from the past and from criticism and suspicion, that he would need more from you in terms of forgiveness and in terms of what you bring to the M, and that you're willing to do that- IF he recommits and agrees to cut contact with OW including cam girls. I think mentioning that isn't critical, it's explaining to him that you won't live with that in your life, important because you are stating you can't move on from something he persists in doing.
But now you move forward. Don't hold your breath. This letter is important in two ways. One, it may lead him back to you one day, but more importantly, Two, it should lead you forward without looking back starting NOW.
Me:38 XW:38 T:11 years M:8 years Kids: S14, D11, D7 BD/Move out day: 6/17/14, D final Dec 15