Don't send the message. Write the message up and then either tear it up or burn it. I suggest sitting on this for a while and then revisit. If you aren't ready for a divorce, then don't push it. You can't fix him and trying to rush the process won't get you what you want, i.e., answers and his attention.
Leave him be and continue focusing on you and your children I would suggest, if you haven't already done so, see a lawyer to see what you and your children are entitled to, but don't share that info w/him.
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.
