I agree with all I would not send the letter....there is too much to edit in it...if you want to let him know about the OW, just tell him....you know he knows you know in his heart, when you bring any focus to the OW it just makes him defend her or their relationship and no matter what you say ....they wont buy it, right now in his mind he has to think what he does to keep doing what he is doing...whe their realtionshio crumbles is when he will see the truth or a closer version...until then you are not on his radar....and this is not about you, its about him, but telling him does no good...