Can hitting people and causing minor injuries be changed from a civil case to a criminal case?

First of all, you can be sure that your father's behavior belongs to self-defense. From a legal point of view, self-defense itself belongs to the category of criminal cases. There is no question of changing from civil to criminal. In fact, your father's behavior belongs to self-defense and does not bear criminal responsibility. Even if the deputy head of the town issues a minor injury certificate, you can't convict your father. Don't worry, it's not a loss. If the deputy head engages in corruption, you can't tell what the judge will do, and no one can prove it. Good luck.