I thought I’d add my story to this. I was in a very similar situation to you. Long marriage, no affection. Was unhappy for a long time.
Two kids of similar ages. H, who was not a bad guy and loved his kids and works hard for them.
However, when I initiated separation - it all changed. He changed into someone I have never knew in two decades of knowing him.
And since my divorce happened and also several of my friends’ - this was a consistent theme. Most were as bad, or worse.
The only one situation I saw where it was different was where a guy felt guilty because he had an affair.
Men don’t tend to think of getting tough with monetary negotiations as taking it out on their children. It’s about their anger at you. And it’s about money - in simple terms - he won’t be paying for you longer than he has to.
There is no way he will want to pay for you to have an apartment and continue paying for your life. Once you go for separation - he’ll want to settle finances as quickly as possible so that he can stop paying for you.
Unless there is enough money in the family assets to buy another property - you will have to sell. There simply is no way around it.
You are being very unrealistic over what you want to happen. Or, rather, you are thinking of what’s best for you. While this isn’t going to what is best for him, so he why would he chose to do it? And this has nothing to do with being a good or a bad guy.
I do think the hormones are playing a role here as well. While you don’t sound like a teenager, you also don’t sound like a mature grown up who is able to see the situation realistically. You focus on what you want, rather what is possible or even likely.
I get the need and desire to live your own life. But other than having passionate sexual with other people - what is stopping you from leaving your house and doing things?
You said you spend all your time together. Why is that? Why don’t you start by leaving the house at times and doing things by yourself/with friends? Who is stopping you?
I will also second NOT moving out to a flat leaving him in the family home. A friend did that - her ex used that against her and it took her years to get access to her kids. He was a loving father before then too.