First off, let me say how sorry I am for your pain, but so glad that you found this site. It was literally my life saver and I do not know where I would be mentally without it.
Your situation, as you probably know, is not really that unusual. Some of us do NOT get that truly remorseful spouse, the one that would do anything and everything to make it all up to us. The one that cares about how WE feel every moment of every day and is willing to move hills and mountains to make us whole again.
No, we get the nonremorseful one. The one that thinks that the mere fact that they are still physically here is healing enough for us. They think that 'they' are the ones that have to live with what they have done and never see or acknowledge the hurt, betrayal, and devastation that WE have been thru and are most likely still enduring.
Do I think you should give this letter to your WW? Yes, by all means. Even if she chooses NOT to acknowledge it, which I am guessing she may (the voice of experience here), at least YOU will feel as though you have done your part to make your feelings heard and clear. YOU did not do this to your marriage or your family; she did. She is the broken one; it was all her choice--and it sounds like she is still making that choice by her inability to go NC, the fact that she has still not started IC, that she is doing nothing to even beginning the healing process.
Now the hard part. What do YOU want? How long can you live in a marriage void of love or respect--even if you are doing it for your four children? It is tough, I know all too well. How much can YOU stand? Because I believe you know by now how it eats at you mentally and then physically until you are a shell of the person you once were and then you start to dislike YOURSELF for becoming that sort of person.
Truth be told, there is nothing you can really do to bring your WW around. It is all up to her and has been since she started the A; she is in control of her behavior and she decides what she wants to do. But, do you have to tolerate it? NO! Do you have to continue to wait around for HER to come around? NO! The key is the strength to walk away when you know YOU have done all you are willing to do, done all you can do.
Have YOU had IC? I am there now. My counselor, bless her heart, had also been thru a PA with an OC. She isn't great for the A discussions, pretty much sits there and says things such as 'I don't know how you do it; I don't know how you put up with that.' But, she is working on rebuilding ME, as she has been there herself and did a pretty good job at that. You need the strength to make the decision that it sounds like you want.
We cannot do that for you; we wouldn't do that to you. Only you can and from what I have heard, once you are okay with it in your heart and in your head, it is soo easy to move forward. But you should make a list of questions to ask yourself everyday to get to that point, if it helps. Such as:
-Is this a 'marriage'?
-Can I truly forgive her for what she has done, or at least accept it to the point that I could put it all behind someday?
-What do I deserve?
-Am I only here for financial reasons?
-Am I only here for the kids? And, if the answer is yes to this one and is your main reason for staying at this point, ask yourself this question. What sort of example am I setting for my children and their future relationships? How would I counsel THEM if they were going thru the same thing?
No matter what you decide to do, we will be here for you. We will support you thru thick and thin; we are family. And, if you decide it is time for you to D, then know that we will be behind you, holding you up. But, most of all, remember that if you do D, then you can walk away with a clear conscience, knowing that YOU did everything you could do to help repair the mess that WW made and that you were NEVER the one at fault for ANY of it.
Please take care.