Dear OP
I have read the thread and all your updates.
I hope you can get the help you need.
Please understand that that the majority of men who engage in DV hardly ever change - they don't think they need to. They may talk a good game but ultimately they will not change. Talk is cheap.
You must accept that there is absolutely no future with him.
The initial problem you raised is of course not the actual problem. It's just an obfuscation on this guy's part. He is using the child as a pawn. The child 'prevents' him from working and you are feeling guilty because you don't want the child there.
There is an absolute ocean of red flags waving about this guy. His child is in danger, your dog is in danger and you are in danger. It makes my blood run cold for you.
A lot of good solid research shows that men like this often ending up killing their partners. He's already killed your unborn child. He's well on the way.
Ask yourself: if you had a friend in this situation, what would you advise them? Please be a friend to yourself, and get some support around you.
I'm not in the UK (in Aus) so not sure of the services available but surely police would be first port of call if is he staying with you after having some order put on him.
Sadly, in my line of work I see a lot of decent women who think it's their mission to save these kinds of men. But all it does is train them to continue on doing what they do. Past behaviour is nearly always a predictor of future behaviour. He WILL keep doing this.
Please don't have sex with him. You do not want to be complicating this already very chaotic situation any further. Once there's a child involved the man could potentially be in your life forever, finding ever more toxic means of manipulating you.
I dearly hope you can break this cycle of abuse. You have a job, a home, and a lovely dog. I hope you'll get support from family and friends because you really need them right now. When you can see your way clear, I'd recommend therapy for you, and maybe reading the book Why Does he Do That?.
I'm on the other side of the world but the I'll be thinking of you. Please update and make a good decision for you, your dear little dog and your future.