sand, you should know that abusers rarely, rarely change. The reason for this is that their abusive behavior is (in their minds) never their fault. If you didn't do this, he wouldn't be mad. And since no matter what you do he'll find some excuse to be angry at you, then nothing you do will ever be good enough, and no matter what, it will always be your fault in his eyes. Something for you to consider.
Truth is people can be very deceptive and All relationships include risk. My own father learned this in his first marriage. His new bride did a total 180 on him within just an hour or two after being married. Literally. By the time they arrived at their honeymoon she was a different person, someone he'd never seen before. She became demanding, controlling, mean. All in the time it took from saying 'i do' to getting to their honeymoon.
It's a risk. And sometimes, for some people, the risk pays off. But often times the risks are just that, risks, and don't pay off.
I'm sorry you're experiencing this, it always makes me so sad and angry to hear of people being treated like this in their marriages. And while you are trying to do the right thing, you have to step back and look at what's really going on and ask yourself if what you 'thought' was right is really right.
Everything going on in your home is affecting your children. It's teaching them how to act, or what kind of treatment to accept in the future. There is no 'good' solution for your children at this point, but you have to ask yourself if your children are worse off watching you be abused, and your son being abused, and learning that behavior (or to accept it in their own future relationships) or if they are better off being away from that and enduring the separation of their parents. Personally, i always feel it's better to not let your child, yourself be abused and teach them that it's ok. Put them through the constant fear and belittling.
Your self worth, and the needs of your children should outweigh your desire to not have to own up to the situation your in because it's become something you never wanted.