Pianoman,
I'll take a crack at your questions. I have been here a long time and a few have tried the "file for divorce to wake up the WS". I cannot tell you that it has really worked. However, I will tell you that a few when faced with divorce filings did wake up and realize what they were losing. Most had children of some age that factored into the situation.
Your W may have financial intanglements with you but no emotional entanglements based on third parties.
I think planning to plan B for a year is too much/too little.
How do you like that for a definitive answer?

What I really mean is that you should plan evaluation points while in your plan B. I would suggest every 3 months others might say every month, some 6 months, it doesn't matter. Plan on evaluating how you feel, what has been happening and your PERSONAL GOALS every so often while you are in plan B.
You will file for divorce when you are willing to, no matter if you are ready. You will know when it is time. She has treated you poorly, and with plan B you will find that this poor treatment coupled with her decreasing influence in your life will lead you to reassess with a clearer mind.
My bet is that one of two things will happen, one the affair will end and she will test the waters with you. If she does, it is not enough that OM is gone. You and she need to understand why she thought this approach was a good idea and how she justified hurting you so badly. Affairs are in and of themselves very selfish acts, and you really need to consider whether remaining to such a woman is in your best interests even if the affair ends.
The other thing that is likely to happen is that you will find other parts of your life more interesting, you will find other people more interesting, you grow tired of holding yourself back from life and eventually you will come to the conclusion there are more fish in the sea and there are women out there to share your life with that would appreciate and want you in their lives. At that point you will find your decision to plan D and end plan B will come naturally.
Pianoman, you MUST understand that these things are predictable and have a time line that is amazingly consistent. Your plan B will hurt YOU far more than she will hurt because she is in the depths of her A. As everyday life starts to intrude, she may come to miss what you brought to her life, but it will be months before that is likely to happen.
Plan B is risky, but necessary for your mental health and ultimate ability to make a clear headed decision. Keep to it, but as others have said, work on your life, your interests, your friends, and yes your family. Build your life, enjoy it, and I can tell you that it will work out one way or another.
I have been on this orb for a long time, and one thing I have noticed that whenever I was confronted with a big decision, it ultimately was no decision at all. The data made it clear which way to go and what to do. I suggest you look at the data, not how you wish it were or what you want it to be, but just the raw data. You will know how and when to make your decisions.
You really cannot force these things. Focus on your life and the data.
hope this helps.
God Bless,
JL