Hey BlondeQT, now that he's decided to be with the OW, don't you give him another thought! Put it out of your mind, or you're going to be negative and miserable and in pain. If anything, them being together will hasten the end of their relationship.
It seems he's on top and you're at the bottom, but that's going to change because his life with her will only be OK to a point, and that's as good as it's ever going to get, while your whole life is an open canvas now and can become great if you make it so. He escaped a relationship just to be in another... meet the new boss, same as the old boss... you grow as a person during this time and focus on yourself and don't use up your brain energy dwelling on him.