I want to second the idea of not giving in.
She may be the love of your life, but please....please.. please.. dont teach your children that relationships should be like this.
Dad should not be constantly hurt by Mom.
Mom should not run away from kids and Dad.
Dad and mom should be friends, lovers, and be respectful of each other.
It is hard to do, but take a break from that relationship for a while.
Maybe she needs to too and that is why she is doing what she is doing.
Give it some time with no sex.
DID you hear that? NO SEX ( between you two...)
Give it a year. See what happens.
But in the mean time.. do talk to a lawyer. If for nothing else other then establishing and learning what a divorce would be for you to be a step ahead of the game.