The short answer is because he wasn't always like this, because I do genuinely think he's depressed and burned out, and because I hope that there's a chance that in time he'll straighten himself out. As he is today, no, I don't want him and I deserve better.
They all were. If they were all like they are now, then we would not have married them. And that person we married is still there, buried beneath the hurt and the resentment and the anger. But the thing is, only they can find their way out. You can't fix him. You can only fix you. So, sit with his hurt, his anger, and his resentment, but do not let it become a part of you. Understand that, rightly or wrongly, you are the focus of his pain. The more he sees you, the more pain he is in.
Alison, it is not just them in a fog. We too are put there, whether we like it or not. Your last entry suggests you are coming out of yours. Leave him to his. What is important is that you heal and that your children feel loved and secure. That is all that matters right now.
Yorkie is right (isn't she always) - you are doing well.