Ian - It has been a long time, and I was hoping that no news was good news. I am sorry to hear about the turn of events, and how she told you (after the fact). Also seems that Ross already knew/she told him before you were informed, so he has already been placed in the middle.
I know that you are a great dad and will continue to be there for both kids, no matter what. We can't make our children's other parent be better people, unfortunately....