"What does he want me to do? Be trapped in the house all day as I can’t afford petrol or activities?"
Yes. Yes, that is exactly what he wants you to do. Remember, you are not family in his eyes. You are a skivvy and a domestic appliance and a subhuman and probably a whole lot more in his eyes. What you are NOT (in his eyes) is an equal partner in a relationship.
He is attempting to control you by financially abusing you.
SIGN NOTHING.
It sounds as if he is significantly ramping up his controlling behaviour, possibly because he senses that the scales are falling from your eyes. He's putting effort into getting you under the thumb NOW so that post-birth you will be so sleep-deprived/distracted/isolated that you will be very easy to control.
What do I tell them now? We’re not moving as he is trying to blackmail me into paying for a cleaner I can’t afford because of his obsessive desire for a clutter free house?
"I genuinely feel like I’m being massively gaslighted as he puts such a convincing argument over why I should pay or we don’t move even though it’s him that has the impossibly high expectations."
The 'convincing argument' concerns me. He is grinding you down. His behaviour is unreasonable, but he bamboozles you - yes, he gaslights you - into thinking that you are the one in the wrong. I think it is time for you to remove yourself from his 'convincing argument' as to why white is black and up is down. Please know that I absolutely believe that he can persuade you that unreasonable is reasonable. He's been softening you up for quite some time.
I think you should consider moving out ASAP. He will continue to drip his poison into your ear, and the sooner you are away from that, the sooner your head will clear and you will stop doubting yourself.
"We’ve told friends and family were moving. What do I tell them now? We’re not moving as he is trying to blackmail me into paying for a cleaner I can’t afford because of his obsessive desire for a clutter free house?"
Pretty much, yes. Do NOT be put off leaving him because you don't know how to tell friends and family. Most people are smart enough to know that what they see of other people's lives is a snapshot, an image, a facade - and that the reality can be very different. Be HONEST with them, you may find priceless support from them. You will certainly find out who your real friends are, and they're the only ones that matter.
But please - accept this is who he is and it will not change, and you do not want to be the third woman whose life he fucks over.
Leave. Leave ASAP.