Bluestar is right... if you refuse to sign the divorce decree it will have to go through certain channels but your H will still divorce you and you will get nothing. NOTHING.
If I understand it correctly the new "no fault" guidelines aren't going to be available right away and they are still far more stringent than *most* no fault states.
As I see it eventually your H is going to get REALLY fed up and just file. Then you will be forced to answer/respond and legally that will be costly and time consuming. Your H can't even pay the money he owes you now. As the law goes though even if you refuse to sign it your H will still get his divorce. And really, the fact that he has a child on the way should be a good motivator as the court *will* take into consideration the fact that he no longer has just one child to support but two. Get what you can for your son now and let your H go through the process if he wants a reduction once his other child is born.
Each day your H gets more aggressive about wanting this divorce done. I know it's painful but at this point it's the road he is on. Get what you can for you and your son. Get what he owes you. Stop being so flexible about switching visitation and stop driving all over to accommodate your H.
I know you are hurting deeply and for that I am so very, very sorry. But if you stay this course you really will only get more hurt on top of lots of legal and financial stress.