Right, you've made the decision to keep the child, now you owe it to that child to make their life as abuse free as possible.
You do this by preempting anything your ex might come up with. You must inform your midwife, they have a right to be protected from his abuse if he does decide to randomly turn up and try to bully his way into your appointments. They deserve a safe working environment too and it isn't fair to keep this information from them. He has no rights to be at any of your antenatal appointments or the birth.
You need to inform the police of his threats as the midwife may decide you are at risk from harm from your ex and therefore so is your unborn child and may refer you to social services for extra support. Do not be afraid of this, engage with all your heart. They will want to know what steps you are taking to ensure your child is safe. This can be achieved while also enabling your ex to play a part in your childs life. Reporting to the police also shows you are taking this seriously and doing what's best to protect the child and not putting his feelings above your childs safety.
Go to Womens Aid and get all the help you can from them. You've done well to break away from him but there are unacceptable behaviours you are still willing to massively downplay.
Get legal advice so you can have contact sorted legally. Probably contact centres at first and a small baby still dependent on its mother is not going to be old enough for overnight contact, that is in no way suitable and for further down the line. This will prevent any nasty situations form being drawn out further.
Do not put him on the birth certificate, that will give him PR, which many abuse. Look through here and see how many parents are in despair because their ex blocks school moves which would benefit the child, holidays and house moves. If residence has not been sorted legally there is nothing to stop him just refusing to hand the child back and if he has PR the police can do nothing. Then you are in a situation where you have to go to court to sort it, but the longer the delay, the more likely the court is to want to maintain the current status quo and not disrupt the child further.
Although mediation may be suggested, its always advisable not to engage in mediation with an abuser as they often use the setting as just another opportunity to exert their authority and brow beat you in to getting what they want.
Everything has to be approached from the view of what is in the childs best interests. Sometimes they will coincide with his wishes and sometimes not. The more legal framework you get in place the easier things will be in the long run. Hope for the best by all means but please prepare for the worst.
We don't want to see you post on here in a couple of years having gone along with his wishes to keep him happy, thinking it's also what's best for the child and he's now decided for some frivolous that you're an unfit mother and is refusing to return the child, the police are saying they can do nothing and you have no idea where your child is because the ex has spirited him away to relatives in the hopes that things take so long to get sorted in the courts that they decide it's now more of an upheaval to return the child to you.