First, if the two of you were to get divorced, the kids aren't going to come into consideration since both of your kids are with other people when it comes to asset division.

And he has been planning on filing for divorce for a long time, he just wanted to keep most of the marital assets. Did he agree to waive his interest in your 401K, life insurance, leave some to your kids in the divorce? Probably not. And if you signed it before he filed for divorce, he would be able to go after your 401K but you wouldn't be able to touch his.

My suggestion is to contact a lawyer (his attorny is right, she can't advise you. She's his lawyer not yours. At least she was ethical enough to let you know this) and file for divorce before he does. Put him on the defensive. If he wanted a divorce, he should have just come right out and said it rather than try to get a settlement that is not fair before doing so.