Kyh - I am so sorry. You are right, your children don't deserve this; no kids do.
Obviously, it's most concerning that this schedule cannot be maintained come fall and that she just assumes the kids will change to a different school and live with her. I think it'll be time for your lawyer to help you navigate those waters.
You didn't choose any of this. Someday your children will understand this. I wish I had some great advice to make it all easier.
Me 41, H 47, M 15 yrs, S11, S13 BD 1: 11/4/14 we work on it; really I pretzel myself BD 2: 3/31/15 H goes down to "dorm room" 8/15: H back to MBR 10/15: H back in dorm room 1/18: H files, now divorced