The Guarantee Clause of the Constitution requires him to do his duty. He knows there was fraud. He also DOES have unilateral power to count whatever votes he wants. The Constitution grants him and him only the task of counting the votes. Not reviewable, not disputable, not challengeable. Full and complete authority.
He chose not to do that. Instead, he punted to Congress instead of doing what he was constitutionally required to do. Pence is done. His political career is over. This was MAGA suicide for him and he did it anyway. And I would go so far as to name him a traitor.