You know, when you write about your kids, it makes me realize that I'm mostly concerned for the kids in all our situations.
I admire your 17 year old's wisdom.
I sense your 13 year old is getting there.
It was fine for you to tell your 13 year old what your W was doing was wrong. You might even add that's why you asked her to leave, because she was cheating on you. Your daughter probably already knows it.
Now back to you. You need to be OK for those girls. Not only to be a provider, but to be the emotional and spiritual strength they need. Your wife has thrown them some serious curve balls and they need you.
The hard part for all of us is letting go of the notion we can stop our spouses from throwing the curve balls.
As you approach your birthday, I'll celebrate you.