"The bast@#$d got my W and now he wants my D8 too, and I should just let it happen?"
Now you're making stuff up in your head. You don't know what the extent of their interactions were with your D and it's your W's choice to bring your D around him. This is about you and your W. All he wants is to get in your W's pants.
Like I wrote earlier, this is what you need to do -
"Talk to a L and find out what your legal rights are. Then stop enabling her. Stop helping her. Stop making excuses for her behavior. Stop giving her money. Stop planning things between your D and her. Tell her that you will not live in an open marriage and that as long as OM was in the picture. If she threatens you, tell her what the L has told you and that she can have the papers filed because you are done and the OM can have her."
So what have you "stopped" doing?
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.