I'm going to be blunt here....if you think this (What I am saying is if she thinks it is safe enough to stay, then this guy is bluff.) then I have to wonder how many people you've known who have truly lived in abusive situations. It seems so very black and white doesn't it? Abusive situation.....leave! Unfortunately it just often isn't so simple because there are factors such as fear, unpredictability, and irrational behavior to consider....add to that combo the fact that her H has a history of not controlling his anger and BOOOM!
My 1st H was VERY abusive, I stayed much longer than I should have for a variety of reasons.....one of which was the fear of what would happen if/when I really tried to leave. Yes, most of the time her H may be bluffing...just as my XH was, BUT he's unpredictable....and when threatened or feeling like he's losing control over things, is likely to snap.....he did this once before when Chrissy tried to leave.
Chrissy, IMPO....because your H has behaved this way to you in the past, I would really recommend that at a minimum you have the police present when you are leaving, for the protection of you and your children. Your H won't be likely to do anything with cops already there. As you stated before, they are already aware of what your H is capable of....with them there, he's more likely to behave....thereby making your exit easier.
I did this with one of my best friends who was trying to extracate herself from an abusive boyfriend. She happened to work with me....she came back to the office after going home at lunch and was an emotional wreck with bruises about her neck. We immediately left the office and went and got a restraining order. When we had finished that, we drove back to my office and called the cops to meet us. They (2 big male cops) followed us over to her house....and stayed with us the entire time while the cops escorted him out. Actually they ended up escorting him out with handcuffs, because he had already left bruises on her (drug her out of her car by her hair earlier that day).....but had he behaved while we were packing his stuff....he might have had an easier time of things. Although the cops didn't realize she actually had bruises at first....then they were obligated to arrest him....anyway, I digress.
Looks like it's going to come down to you and the kids leaving since you stated you have no reason to want the house....so having the cops present will be definitely to your advantage. That way should he snap and get out of line....they can handle it for you.