How do you decide to leave?

Sketch out parallel futures with him and without him. Your children, if my math is right, are now 16, 14, and 12. Even the 12 knows you are not happy and probably, if honest, they all would say that they would rather you be happy than having two parents in the house. They will pull together with you to run a house should you leave and take them, so don't let the children be a factor in your decision. Thinking of your two parallel futures, ask the old Ann Landers question - am I better off with him or without him? The answer will show you what you should do. Best of luck to you, teacher of the year. I wish he would prize your singular and impressive accomplishments more highly.