[quote Beachshell]@MrsWombat
Thank you. This is exactly my point. It’s about security for me and my child. His proposed arrangement works very nicely for him, but puts me in a precarious position. He’s not losing anything by me and my child living there, in fact he’s gaining monetarily by having half of all the bills paid. Plus the other things mentioned; childcare, cooking, cleaning. Which by proxy often falls to the woman. I also wouldn’t expect a boyfriend to contribute more than half the bills if I was the one with the mortgage and suggesting he lived with me, whilst being fully aware of what he’s sacrificing (security, furniture, longer commute). In my mind, I’m paying the mortgage anyway as it’s my asset and something for my child to inherit one day, why would I ask someone to pay half of that? If I want a ‘partnership’ I’d be proposing buying a property together or marriage 
I like the idea of putting the money saved into a savings account that can be used for if/when we buy a future property together.[/quote]
I think you should turn it around and and look at how much he is gaining by having you move in. At the moment he seems to be acting as if all the benefits are conferred on you so you should have to pay up.
But as you've pointed out - you are moving out of nice flat, with security of tenure, convenient for your work and presumably childcare that allows you to work.
He earns more than triple what you do but wants everything split 50-50%
Including much more expensive bills than you currently pay that he chose to take on, which you would not have.
Is he putting enough value on your contribution to things like housework, a second adult to help out with his child. What are his current arrangements, cleaner, childcare? what is he saving by having you do these tasks (It's a slippery slope really because his it sets a precedent for you doing all the "wife work" because you should be so grateful to live there and at the same time pay half for everything)
So if you move in he gets:
50% of his 4bed house mortgage
50% off all his bills including luxury ones he chose
Convenience of staying in his chosen house and chosen location.
No change to his travel to work time.
No need to pay for his furniture in storage.
Almost full time housework, shopping and cooking and childcare which you have already conceded in earlier post mostly falls to the woman by proxy in reality.
Another adult around to help out with his child
No change in his security or rights to stay there.
100 per cent of Appreciating asset, which he will only be paying half the costs towards. Yes you do pay rent to a landlord, but he is not a landlord as you will be surrendering rental rights.
No one is suggesting you live for free or don't pay your way, but if you turn it round he has lots of benefits which he is not putting a value on when he insists you pay 50% for and he will not be splitting the labour.
It is true that everybody gives up some things to move in with someone else and usually the benefits outweigh that. All I'm saying is there are a lot of hidden costs for you which he just doesn't take into account.
But are you sure you will be happy with carrying those all "costs" in the long term? Once you have moved in, will it get easier or harder to make him see things from your point of view and meet you halfway? Contributing 50% to a more expensive living arrangement will means your opportunity to save for your future will take a big hit, whilst his unallocated income, already triple yours will have had 50% of expenses cut. Doesn't sound quite as equal now as someone saying we should split everything down the middle. How will taking on most of his household and childcare responsibilities impact your own career progression and pension?
I think you have more discussions ahead before you can feel comfortable giving up your independence and security to move in on his terms. He sounds inflexible and as if he has his own interests as a priority rather than fully understanding shared interests.