inahaze-
just a warning, leaving is a dangerous time. mine became violent when i left. i'm sitting here with a fractured shoulder as i write to you.
if possible, do what you can to organize your move prior to telling him. why live in an uncomfortable, volatile home when you don't need to? keep your cards close to your chest, do your planning and be careful who you tell, as most people cannot keep a secret.
and try to avoid getting angry, as it might be possible when he pushes your buttons, that you will blurt out your plans in anger.
when you do tell him, perhaps after you have your new place established, consider having a third party present or like hydrogirl says, do it in a public place.