I'm really proud of you. I wish I had done what you are doing - you are exactly right on IMO. My H strung me along for many months, even attending MC in which he didn't do anything. But I guess it made himself feel like the good guy. But all he wanted was the legal separation papers signed. The week they were signed, he told me he's not coming back, has a gf (which he had had the whole time) and is buying an airplane.
They do not respect our boundaries, they are emotionally abusive, and they do want to tell themselves and the world they are good guys. It's the MO. I finally see that now. YOu are strong and I support you 100%.
I haven't written a NC letter - because I haven't sorted out stuff with our child. ONce the legal protective order is in place (which is as hard for me as your NC letter was) I'll know he can't manipulate me on that and I may consider the letter.
Anyhow, keep strong you are doing the right thing. I am amazed how much I feel emotionally and mentally better when I don't talk to or see him. I can finally think my own thoughts, feel my own feelings without him and OW invading my soul.