LD - Be strong. What you are doing is setting boundaries. Your W may not like them but she will respect you for them. I doubt she will respect you at all in the future if you allow this affair to continue unabated and on her terms. She doesn't respect you or the marriage right now and that is obvious.
She has to feel and understand that there are consequences for her actions. I think at this point it sounds like you have been enabling your BIL and your W to continue in some very screwed up behavior.
Perhaps you need to take her belongings and put them in bags out in front of the house...along with the BIL.
You don't deserve to be treated this way. Why put up with it? If she is going to come back, that is what she'll do, regardless. In the meantime you need to make it clear that you won't be a doormat.
There has been somewhat of a change in my ExWs behavior towards me. You see the marriage is over and I'm getting out of the house. I'm free and she has no control or game left. After this I will no longer exist in her world...and she knows it. Marriage in practical terms is just a piece of paper. However the relationship either endures or dies. Reality is a bitch. My ExW thinks she could walz back into my life at any time but she is starting to lose that feeling of control.
Your W needs to feel like she is losing something in all this in order to change. The only way that is going to happen is if she loses control and connection. To date she has had you right where she wants you. She comes and goes as she pleases and knows your every move. There is some gamesmanship here unfortunately. I'm not into games but sometimes you just have to play. This is no time to lay on the ropes and counter punch. Start moving and throw a few well timed combinations. Shake things up a bit. Change your rhythem and timing.
Me- 47 W- 45 Married 22 years Together 30 years No Kids, 1 dog, 1 Cat 2005 - 2007 W in MLT 1/08 - Crisis hits 3/08 W drops Bomb and leaves in the middle of the night. Admits to PA 4/08 W files for divorce 8/08 Divorce final