Seperated is seperated and divorced is divorced. He's going to have to pay child support either way.
If you seperate, you keep your benefits but you can't remarry until (your or him) you get a divorce. He may figure this out and ask for a divorce just to screw you. Sorry, just being honest. I hope it doesn't happen.
It really benefits you bc you keep your benefits and you won't be held legally responsible if he drives drunk and kills someone (God forbid). You may get higher rates on your car insurance as your not married. Maybe someone has more to offer.