Wandererr,
You could just belittle the feelings you're having -- that you don't want to make it work any more, that you've lost what you felt for him -- but that's just keeping both him, and YOU, from moving on to lives that better suit you.
How did I? I identified where all of my important papers were in my house, and hid them in a special file. I separated my finances by getting my own bank accounts, and started diverting all of my own money into them. I got MY things in MY name. (all of this without making a fuss of it) I found an apartment. And then I told him, very clearly and calmly, what I was going to do, and why, and waited for the worst. I planned to move out in a month but ended up moving out in a week because of his verbal abuse, which was six days longer than I should have.
It sounds like he might be a control freak, so if I were you, I'd check out the battered womens' resources in your area first, in case you have to find shelter. But the thing that will freak him out most of all is if you waffle, say things like "maybe if" and "if only", which are signs that he can change the outcome by manipulating more. Threatening to leave him when you don't actually have any intention of doing it is cruel. Actually leaving him, while painful, at least removes the possibility that he can do or say something -- for a few days or a week -- that will make it all better again.
No one can tell you the right thing to do. But imho, you're not doing anyone any favors by staying in a relationship just because "you get along pretty well." An XABF was shocked when I left, because, as he put it, "I've never beat you up or anything."
As if that's all we can expect out of one of the most important relationships of our lives.
You deserve better. You deserve love, and respect, both giving and getting. But you're going to have to jump through a couple of flaming hoops to get there. There are a lot of us here who would tell you that it's really, really worth it, just to get off the rollercoaster and find a life that makes you happy to wake up every morning. But it's really your choice. Do you think you're worth it?