I've been in a similar situation, but wasn't pregnant. I did not pursue with the police and wish I had, as I was terrified at the time. I was stalked for a while after, but after about 10 months of no contact it stopped, although it may be different for you. This guy made threats to kill himself, assault my family, set me on fire, called me names etc, anything to get me to contact him. It's only later in life i realised this guy had BPD and was probably quite ill. I still can't help but feel repulsed by the thought of him though. I would read up on BPD as it helps you understand that it's not anything you've done that's made this happen. He will make you feel defective and a horrible person, but he is just projecting how he feels about himself on to you.
There is a chance that he will eventually give up when he is not getting any response from you or meets someone else, but you are doing the right thing by involving the police and documenting the abuse. I think if he has a history of DV, SS would be very reluctant to allow him to have contact with the child on his own, but it sounds like he is using the child as an excuse to maintain contact with you and to continue to be abusive. Does he already have kids? On what terms does he see them?
Is it possible to move away for a bit closer to your parents and friends after the child is born, or are you very much committed to work? Could you possibly move out of town and a bit closer to them. It must be hard going through this on your own and having them around will help. I know the feeling of looking over your shoulder all the time, and being away from where you currently live might help, but it doesn't completely go away. I still worry about bumping in to my ex and I last saw him 15 years ago!
You have absolutely done the right thing by ejecting this guy from your life. He is not in a place mentally where he can be a good partner, let alone a father. I hope it all works out for you in the end, but please stick to your guns and don't let him guilt trip you. He needs to accept that his past and current behaviour demonstrates that he is not in a place where he can be a father and has to prove to you otherwise.