Hi, thepainisreal,
I'm so sorry you're going through this. I understand your trauma; I do. I, too, was completely committed to reconciling, and went 100% into the "pick me" dance. I was unbelievably understanding and kind to her while she decided what to do. And I told almost no one, to "protect" her. The result was an abysmal failure--my behavior only gave her time to get her ducks in a row and leave me for him.
Turns out, my fears were all about me. I felt abandoned as a child, and would now do ANYTHING to avoid that feeling again. She was doing what I feared most: abandoned me (AGAIN). It reinforced the notion that I must not be loveable, which eviscerated me.
Now, NOW, almost five years later and after a ton of work, I'm in a new relationship with someone who just naturally fits me so well, it's stunning. And all the trauma, shock, and agony through which I journeyed make me appreciate and love her all the more.
I hope that some lessons I learned FROM DOING EVERYTHING WRONG, may help you. First, the not disclosing what was happening to all harmed ME. As my IC said: "Secrets beget shame. Keep them long enough, and the shame becomes you." My resolution to move on became stronger when I heard that; I wasn't going to be further harmed by choosing to carry that burden. It turned out that telling my kids and OBS was ESSENTIAL to my healing.
Second, you cannot "nice" her back. A marriage takes two; as much as you love her and want it to work, you can't do it by yourself. She is addicted to her affair, and being nice isn't the way to get her out of her addition. In fact, it ENABLES it.
Third, your wife has changed via her affair and the choices she made. I couldn't believe the person I married would do this. unfortunately, her affair had changed her--she was no long the person I had loved.
Fourth, more to the point, she never really was the person I held her up to be. She was very good at deception, as it turns out. I was very good at accepting that deception. It worked for a while.
Last, you WILL survive this, and come out better for it, whether you R or D. Know that her choices have nothing to do with who you are.
Ultimately, as much as we might have loved our spouses (and I absolutely did; failings and all), you cannot hold a marriage together by yourself. It takes two. And if she's unwilling (because she's addicted to her affair and has changed because it) there is no other choice but to protect yourself.
I understand your feelings; I really do. I had them, too. I can only say that the only hope for your marriage, is to act on what the good people here offer. You cannot treat an addict gently and hope they'll change. (Even with that, they may not change.) Being the most understanding and nice guy on the planet, unfortunately, guarantees that she won't change.
As hard as it is to imagine, your strength in dealing with her is the only hope your marriage has. She still may be too far gone; if so, there's nothing you can do about it.
But even if the "worst" happens, and your marriage is over, please know that YOU WILL BE OKAY. There is life after a divorce. It takes years of work and recovery, but there is life. In fact, there's strength, love, compassion, and joy like never before. I expect you don't know that now... Take it from those of who've been there. It will come for you.