I've come very late to this thread and everyone has already said what I would have done ..... but frankly, my overriding impression after reading this thread was one of fear, even though I, quite obviously, am not the one going through it and being treated like this (and sadness too, that so many others have admitted to being treated similarly).
Whether or not this behaviour is due to underlying mental illness - or whether it's "simple" abusive bullying - the point is that it's totally unacceptable, and it sounds as though you have put up with it for long enough. You are being treated like something on the bottom of his shoe .... being belittled and devalued ..... your children are being affected too.
If you are - practically, financially and emotionally - in a position to extricate yourself and the kids from this "man", then please do it, for yourself and for them. You shouldn't have to take this sh*t for one moment later. A separation doesn't have to automatically mean the end of your marriage - for example, the shock of it may just prompt him to seek some sort of professional help, be it counselling and/or anger management etc, and who knows, there may be some sort of future for you as a couple, providing he accepts some responsibility (well, most of the responsibility) for what's happened. However, the most important thing IMO is that you and your kids get yourselves into a place, NOW, - literally & emotionally - where you can actually relax and get on with your lives, without living in a perpetual state of fear and anxiety about when the next outburst will take place, or when you'll next be made to feel worthless.
I feel so sorry for you - and any other woman (and children) having to deal with something like this. It goes far beyond the odd bit of sniping or bickering .... and because it is so beyond the boundaries of what is usually considered acceptable behaviour between a couple, it must also be very frightening (and frustrating, humiliating, upsetting, baffling etc etc).
I hope you find the strength to leave and place yourself in a position of strength.