Barb - since I just lived this - right down to the text messages when he was "supposed" to be with me, I want to offer you some advice that you probably don't want to hear.
First off, an affair is usually like an addiction. Nothing logical is going to sway him out of his mindset. The spark from a new relationship releases endorphins that give a temporary high. Also, since your husband cannot cement his relationship with OW as long as you are around, he has her and his relationship with her built up in his mind as his perfect fantasy.
If you can find a way to force him to get rid of her, it will do you no good. Why? Well, because then he had a leave when he didn't want to and for the rest of your time together you will be competing with the "perfect" OW than he had to leave behind. And as long as she is what he wants (or think he wants), he will NOT show up for your marriage.
The only way to "fix" this situation is by rolling the dice - let him go. Most affairs don't last 6 months beyond the spouse discovering the truth. Once he has an opportunity to spend all the time he wants with the OW, he may find he still thinks she's perfect and you lose. BUT, the fog may clear and he may start to see her for exactly what she is - a whore that he could never trust because she's willing to have an affair with a married man. And her perfection will start to wane as soon as normal lifes problems enter into their relationship. After all, an affair is all about only seeing/spending time/talking about things when you're both at your best. As soon as bills, broken cars, sick kids, etc. enter in, the fantasy is over.
In my opinion, the only way to truly have a secure future with a cheating spouse is if they CHOOSE to give up the other person in order to be with you.
