Child support in NJ

I'm married but not living with my husband. He abused me while pregnant so my parents made me move back with them. After I moved out all my belongings, he disappeared. I have no idea where he is living now. Eventually I want to file for divorce and custody and child support. But how soon can I do that? I was thinking about getting a lawyer to do everything all at once. How does it work? I'm working and I make 2500 per month after taxes and he makes 3500. Also, I'm thinking about quitting my job a few months after the baby is born. Should I file for child support after I leave my job or right away? Can the amount be changed later if I do decide to stop working?? Please help