Go to the infidelity section. Page 230 titled "The Ultimatum".
The approach there is about the equivalent of what some great posters that are no longer here would basically put forth. If I had it to do all over again I would use that approach. You don't have to use the file for divorce part, but you could make her move out of the home. After all, you are here to try and save your marriage. BUT that's your choice to make and you don't want to make it out of anger.
Also, the evidence you have is YOURS don't show her your cards, because she could "say" she will end it and then knowing how you found out, hide that from you even better or go a new way. So the evidence is for you to firmly tell her that YOU know she's having an A.
Your W will more than likely turn into a Demon when you do this, but you have to stay strong and not engage with her spew. You have to be firm and confident when you tell her this. Like a man that loves his Wife, but loves Himself more than to tolerate an open Marriage.
The rest of Divorce Remedy is about identifying what you can do differently about YOUR part in the marriage. What did she find in the OM that was missing in you kind of searching. Basically, she will have to decide between losing you and going with the OM. She will more than likely pick him, but if you do this correctly you will eliminate her "Fantasy" and make it not so fun anymore. Plus you will look like a pillar of strength.
Once this part is done, YOU have a lot of work to do on yourself.
