There are four possible outcomes:
1. You leave him. But you don't seem to consider that an option.
2. He leaves you. But he seems happy enough with the relationship. He gets his way, and if he doesn't, he is free to abuse you until he feels better about himself.
3. He changes. But that won't happen, because he is happy the way he is.
4. You change.
So if you're not willing to leave him, then you need to make the best of a bad situation by just accepting it. Take all the abuse that he gives you, because at least somebody is paying some attention to you. Accept playing second fiddle to the dog, because that's just how it's going to be in this relationship. Sure, the dog will die long before you do, but he can always get another dog. You, however, cannot have a cat, even though you want one. So stop whining and just accept your sorry lot in life, because that's what you have chosen for yourself.