questions about divorce,please help

our marriage come to an end, we both agree for a divorce.
the question is, I have some savings and he doesn't(he just get a job recently),he agree to not take my money and would sign a paper, does that have legal power? can he go after my money later in the divorce process?
we have a little baby, he is not willing to pay the child support and I will have the full custody, can he ask for the custody later?
thank you.