I think that some of the posters might be frustrated, because weve been through what you are going through, we know the results in doing the things that you want to do, and yet, we cant seem to arm you with the knowledge that you need.
No, dont send that letter. No, dont have that conversation.
I think you should reread the detachment thread (or read it if you havent). Before worrying about closure and moving on and all this other stuff, you need to take back control of your own emotions. Right now, you are still getting bounced all over the place by your W. You point out several times how much you are hurting. Before worrying about your relationship with W, you have to stop the bleeding.
Detachment is what I believe is that state that you can achieve where that spout is turned off. You get to a place where you are emotionally stable. Where highs and lows of your interactions with W dont impact you. Thats done through GAL. By embracing new opportunities to fill your emotional bucket with positivity NOT FROM YOUR W.
All the stuff you are putting in that post above is you trying to get her to fill that bucket. And I guess your thought is that you want to give her one last opportunity to do so, before you are willing to accept those positive feelings from other people. My advice is, instead to first focus on filling your bucket through your GAL activities, and THEN youll be in a much better place where you dont NEED your W to fill your bucket.