You may want to consider making a separate recording of her VM, just in case it is needed some day if this goes to court. And, you may want to print out the calendar every time she changes the scheduling. It will show how unstable it would be for S12 living with her.
I don't want to sound mean, HP. Over the years, I've picked up a couple of things here on the board about how one should protect themselves if they have to go to court over child custody.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!