I'm sorry to be the bearer of bad news but, while he can't stop you from moving out, as he shares parental responsibility with you the father of your dc can apply for an emergency ex parte Prohibited Steps Order to expressly prohibit you from moving your dc from their current home/address.
This, of course is not to say that he will make any such application or that he will be successful but if he does, and if he is, you're unlikely to be aware of it until the order is served on you.
However, please DON'T PANIC as, if he's making this threat in response to your plan to move out with the dc, there's every chance he's bluffing and you're best advised to be as cunning as a barrel full of monkeys as he is.
To this end I suggest you avoid making any further mention of your plan and, if he is aware of your appointment later today, give the impression that the property you're signing up has unexpectedly fallen through or that there is some delay in the proceedings, as once the deed is done and you have moved into your new home with the dc he won't be able to force your/their return.
Don't worry that you'll lose your 6 months rent money as an emergency PSO is merely a means of ensuring that the status quo is maintained pending a further Court hearing at which both/all parties are present and, should you be served with any such injunction, you can challenge it before the date for further hearing that will be shown on the order which is customarily within 28 days of it having been granted.
That said, I reiterate that you have NO NEED TO PANIC as emergency PCOs are, in the main, used to address situations where the welfare of dc is at risk and, as I can't imagine that a judge would grant such an order where the respondent is taking the dc to live a short distance from their present home because she is being abused by the applicant, it's probable that he may have to lie fudge the truth of the matter in order to temporarily prevent you from moving out with the dc and this will inevitably count against him in the longer term.
I hope you've stayed with me so far and can accept my assurance that, should push come to shove, you will prevail and can be confident that, one way or another, you and your dc will be moving into your new home on or around the date shown on your tenancy agreement.
A guide to emergency PSOs and other injunctions can be found here: www.ncdv.org.uk/are-you-suffering-domestic-abuse/how-the-law-can-protect-you/
If you have any reason to feel in fear or danger of what your h may do to you/your property/himself, please don't hesitate to call 999 and, when they arrive, ask the police to remove him from your home.
As the national helpline is often oversubscribed, you can find your nearest Women's Aid service here www.womensaid.org.uk/domestic-abuse-directory/ but it's unlikely to be available 24/7.