"... growing up walking on eggshells is a horrible way to live and will affect your children."
^This. Oh, so much, this^.
Perhaps you need to spell it out to your husband that he is hurting his children with his behaviour/attitude. Ask him if he understands that 12, 10 and 8 are still very young ages - and that his daughters actively need him to show them what not to end up dating/married to when they're older. That his son needs him to be a decent man, husband and father so that he can model himself on that example when he, too, is older. Tell him that they hate living with the atmosphere which he creates... that you aren't a fan of it, either.
Of course you shouldn't give up on a marriage at the (hopefully temporary) say-so of children... but you should listen to them, and understand why they feel the way they do about their father 
I grew up with a father who spent long periods of time away from home - and there were times whenhe and my mother made family life absolutely miserable. But overall? My Dad made time for me, as his only daughter. Even when I hit puberty and became argumentative, as I think we all do when hormones first start to swirl around, I always knew that my Dad loved me. We still spent time together without my mother or my brothers around. Even now that I'm an aged parent myself, my Dad and I still make time for one another. Conversely, I don't have a relationship with my mother, for various reasons. Primarily, though? Because she was the one who made our home-life hellish, with moody and deliberately mean behaviour... Not one of my mother's 3 children have anything to do with her. My brothers went NC years ago, and I have very recently. The relief of not having a constant feeling of dread hanging over me, is actually immense.
Your husband needs, desperately, to work on his relationship with your children, OP, before he actually loses them. Fairly soon, they'll be old enough to vote with their feet - and whilst they'll probably continue to have a relationship with you, they may well choose not to, because of your husband, I'm afraid. 