I'm glad you stopped replying to his absurd e-mails. I do not understand such insane behavior on his part! And did I get this right - he apologized for the e-mails, but then later went back to his craziness saying he was going to trash talk you to the kids? Yikes.
You are doing FAR better than I would, my dear. HUGE pat on the back!
(((Keep strong and remain the better parent.)))
Getting over a painful experience is much like crossing monkey bars. You have to let go at some point in order to move forward. ~ Joseph Campbell