First, good for you for posting and thinking before delivering the message -- a lot of people don't do that. That is to your credit.
Your speech would be perfect if your W was actively seeking coming back to you. She is not, she has walked away. She's not interested in repairing your trust, her actions are not about hurting you, she's not looking to share your heart anymore. She is not looking for your forgiveness! She is not looking for your family to be whole. She is looking for the marriage to end and you are playing into her hand with that speech.
This will not inspire guilt or remorse. When your W hears that speech, she will resent you and be angry with you. If she feels guilty, it will be hidden behind her anger at you.
Here's an alternate suggestion:
Wife, I have valued the marriage we have had together, and I place great value on our family. I know that the marriage has been difficult for you in many ways, it has been difficult for me too. I believe any long term committed relationship will have challenges.
I am also aware that you are having an affair with OM and that it has been going on for some time. I want you to know that I understand how these things happen -- we are all human, we all like the attention of someone new, particularly when we don't feel our needs are being met in our marriage.
Although knowing about the affair has caused me a great deal of pain, I am still interested in working on recovering our marriage. I have made a significant effort to understand the behavior that caused trouble for you, and am doing my best to address it. I'm doing it for myself, as any successful relationship I engage in will require me to be a better partner. If our relationship benefits from my changes, that would be great, but I will pursue them regardless.
I understand that I have caused you pain. I am interested in making our relationship a positive one going forward, particularly for the sake of our children. We've had some very good times together, and I remember and value the reasons that I chose to marry you. At this point, I'm not asking you to do anything. I am going to remain committed to positive change in myself, our marriage and to our family, that is my choice. I'm not looking for a response, I'd just like you to understand how I'm thinking about our situation, and what I plan to do for myself going forward. I wish you happiness with whatever choices you make going forward.
>>>>>>>>
That is detaching and giving her space. That is letting her know that you know, but not making her feel guilty or evil. It's normalizing what she's done. Read these two speeches and ask yourself how you would FEEL if you received them. I would argue that by setting her free, you are "the better man" and will actually make it even harder to live with herself which MAY get you the apology you're looking for at a time that SHE wants to give it.
Good luck
Accuray
Married 18, Together 20, Now Divorced M: 48, W: 50, D: 18, S: 16, D: 12 Bomb Dropped (EA, D): 7/13/11 Start Reconcile: 8/15/11 Bomb Dropped (EA, D): 5/1/2014 (Divorced) In a New Relationship: 3/2015