Tufan,

Can you stop not only helping him with school, but also doing his laundry? I realize that you cannot stop cleaning and cooking for yourself and the kids.

In essence you have stopped giving him the benefit of the doubt. You have resolved to leave him to avoid the misery. But if you stop part of the misery right now, he might grow up to the point at which you will not need to leave him so badly. At least it is worth trying.