Whoah! I've only read your posts OP, and wow did this one stand out!
He doesn't want his son for 5 days because he loves him and would miss him. He wants his son for 5 days because then he would come with money attached.
Way to go for showing who you really are!
Don't get me wrong, the rest of your posts painted a picture of a man who feels entitled to all your worldly goods, simply because you've got more than him. It's clearly not about 'sharing' to him, it's about spending, spending, spending all the lovely money.
"He wants to get married"
I'm normally very pro-marriage, for the protection it offers women once they start having children - but not in your case. Marriage offers you no protection (you sound very financially sorted), and it offers him access to your money, your house - which he will fritter away.
"And he disagrees he is bad with money."
Which is presumably why he's in so much debt. He is bad with money, whether he accepts it or not. And now he's trying to bully you into giving him yours. No, no, no. Just because someone at work made him feel little for not having full access to your money, is no reason to acquiesce. (By the way, I don't actually believe his story. I think he's just decided the time is ripe to start pushing you around.)
"He disagrees that we have a different approach to money though."
See above
! It's obvious you have a different approach to money. Basically, this manchild would say he didn't eat the chocolate even if it was smeared all around his mouth.
Bottom line:
- Don't have joint account with this man, he'll empty it
- Don't marry him, he'll have your house off you
- Reconsider if you want to continue your relationship with a man who, feeling he has you trapped by a shared offspring, is ready to put all those demands upon you that he kept under wraps until now
He thinks you're vulnerable because you've just had a baby. You may be sleep-deprived, but you sound to me as if you've got your wits about you. He's clearly as bad with manipulating people as he is with money. I'd be giving him his marching orders.