What can I do to save my marriage? Help

[Ready2Change]

Let me clarify some of my thoughts on what Robx said: "Agree to the D"

I feel it is better to "NOT FEAR DIVORCE". The sooner you accept that it is a real possibility, the better. DO NOT LET FEAR CONTROL YOU.

What I have seen work:
When the WAS has been unfaithful and is unwilling to work on the M and the LBS does not tolerate that disrespectful behavior and files for D, the WAS is the one that has been rejected and starts pursuing. "I have decided that I will not live in an open marriage. I want all contact with OP cut off immediately. If contact continues I will file for D myself."

Here is another statement, but I feel it will not be as effective as the one above:
"I do not want D. I see many other options. But if that is the only way for you to be happy, I will not stand in your way."