I'm so sorry, but at least you know the truth now. Take a day or two to think about this, and do NOT promise your husband ANYTHING, one way or another. He deserves no answers from you, and you should tell him that.
Let him sweat.
After you've had a chance to process this and calm down, we can all help you with what you should do re: OW's husband. Personally, I feel he has a right to know, so that he can make his OWN decisions that are best for him and his family.
