His update is not surprising. He's after your money OP and perhaps always was. He wants another house bought whilst you were together because first it'll feel more like it's both your place, which doesn't happen when you move into someone's established home. Second, the relationship is on the rocks now and when you split, he'll try saying you bought the house with the intention of sharing it (regardless of it being only in your name and you both not married or he'll want it in his name from the get-go) and try getting some of the house's value like it was a divorce.
There's nothing wrong with being money focussed, that's how you've ended up with the assets you have whilst earning half as much as him! Lots of men who've felt fleeced in a divorce (whether they have or haven't been) refuse to marry again or have joint finances, to prevent it happening again. You're not being unreasonable. You've been burned once, you've got a life you're happy with, a partner should add to that not detract from it.
You've offered to purchase a house with him jointly, which is messy enough if you split. It's also compromise enough, considering you like where you live now and if you split it would be easy on you because he just moves out, no hassle and no upheaval.
I note that he is still trying to pressurise you. He's slagging you off, accusing you of being unreasonable and of having undesirable personality traits. Yet if he believes that, then why isn't he ending the relationship if he thinks you're that awful? He's still hoping you'll cave. He's totally selfish, emotionally stunted with no ability to see anything from your point of view, just I want, I want, I want and none of what he wants benefits the relationship or you both as a couple at all. It's all solely to benefit him.
It really shows how full of entitlement he is to have even made his initial propositon. Anyone decent would have either stayed living separately because he didn't want to pay you rent and you didn't want him living there without that, then been happy to get a mortgage to share a house purchase with you. Or at least, if hoping for what he wants, a decent person would have waited for you to offer it and split up if you didn't. Only an entitled person has the cheek to actually ask for the moon on a stick, then sulks and gets cross when they can't have it.