All I can tell you is that your feelings will change. Atlas is correct. You are still trying to be a good husband.
You are not her husband in anything other than a legal sense.
Go for a legal settlement. Wait six months or a year after D and then start thinking about your responsibility for her post-D life.
I've never seen ANYONE, WAS or LBS get more generous as time passes. This isn't because they are evil, but because they get less attached to their financial role in someone elses life when that someone else is not in their life.
The courts will watch out for the kids interests.
You watch out for your interests. Like I said, you can always choose to be more generous, but wait until you are in a settled place to make those choices.
Your W is sleeping with OM, living with OM, taking care of OM's kids, f*cking OM. She is not your W. Quit acting like her H.