The best chance to save your marriage is to be willing to end it. I'm serious, you have to accept that you cannot control your wife only yourself. Follow the The 180 degree rules
and Just Let Them Go
. Doing so will show your wife that you will no accept being her consolation prize if things don't work out with the OM (other man). Be willing to convey to her the following and mean it
: "Look wife, I won't be in an open relationship with you, I won't give you X number of days, weeks, months to make your mind, if you really feel like you need to sit on the fence on this decision and can't decide between your affair partner and me well I will make the decision for you, you can be with him because I'm no longer an option. I love you and wish you a good life with him and hope it works out for you because it didn't work out for us. Now the best thing we can do for each other is to make this process as graceful and peaceful as possible for us and our children, I'll contact a lawyer/mediator and get started on the process of our legal separation/divorce."
Your confidence to move on with your life with or without your wife is essential no matter what the outcome of the marriage.