@New Mum to be,
Now you are claiming he hit you and threaten the child in the womb and if so he should be lock up for many years but in order to do that you need some proof of this in order to get your justice.
Did you call the police, did you go for medical treatments as a result of his actions did you tell friends during this period of his actions? Did your friends see you with marks on you also during that time period?
And once more under US laws at least his behavior with his ex is unlikely to come into a court room concerning you. Who know under UK laws I surely do not.
Take a deep breath as without solid proof your claims is not likely to play well in a custody hearing setting and you need to appear completely rational and in control of yourself in family court.
As a non-lawyer it look like the gentleman in some manner is going to be in your and your child life for many decades into the future and fair or not fair that is the likely outcome in my opinion. Hell in the US even proven wife abuse is not enough to bar a man from his child life.
As the women already had stated here talk to a good lawyer.