He's MOVED ON. Which is what you need to be working on (and I know you have been). Whatever his feelings for you, or the dogs, once were, clearly they are no longer occupy his mind or his life.
As much as we love dogs, they are not human beings. They are not like children, wondering why they were "abandoned" by daddy. If you are feeding them and loving them and caring for them, they aren't missing him. They are happy and healthy.