Just wanted to say that I've sent both painful truthful say it all at once letters like the one you shared here, and loving pleading apologizing letters, each being who I was at that time, saying what I felt to say, and I still am where I am, it still went the way it was going to go, and it didn't make it better either way as far as she was concerned.
This really says it doesn't it?
This fantasy we have of finally breaking through, of finally making sense to them, of finally being heard, is precisely one of the reasons we continued taking them back (or coming back). We believed that our case was so obvious that there is no possible way to deny it, and yet... .they always managed to deflect it
For the additional reason of WE needed to hear it, to read it, to say it. To reaffirm it for ourselves, to make sense of what was happening. To find out who WE really are.
If it's best for YOU to send a letter, send it. If it's not, it's probably best to walk away. Easier to do that with the healthiest feet you can, as you so rightly pointed out.
