B, Always count to 10 before responding to his spew. Always remember, that the spew is coming from a place of hurt in a little boy that never grew up. They project so much on to us and the baiting is unbelieveable, but you were great in seeing the hook, line and sinker on this particular email.
Your first priority is and always will be your sons. Your h may express how he felt as a boy, but he really doesn't see himself doing exactly what his father did to him with his own sons. My xh is doing the exact same thing his father did to him and his family, i.e., history repeating itself all over again.
Please, please take care of yourself and those darling kids.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.