The point is that your wife continues to not have any hardships based on her choices. You're paying for everything while she ran around with another guy. Your MIL pays for the mortgage, she really doesn't have to do anything.
If you are adamant about moving out, I would suggest you give her a date, so she knows she has to find a job by then. Then tell her that you will be cancelling her insurance but will keep the kids on yours. She's not your problem any more. And besides, you need the money for your rent.
Also, I would suggest that you talk to your kids. Ask them how they feel. Just because your W is rug-sweeping doesn't mean that you should too.
She needs that dose of reality.
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.