My H has not apologized for the affair, but, like most of your spouses, has apologized over and over for hurting me. I have not told my S about his dad being with someone else; however, my H did sneak OW in to meet my S without my knowledge, under the guise that she was a friend of a friend - YUCK!!! I was mad and he acknowledged that it was not a good thing to do and apologized for doing it.
I too find that if he is in good with OW, he is affectionate towards me; he wants to see me more, etc. However, case in point last night, if things are not so good, he doesn't want to be around me. That hurts too.