What is the ruling on a father preventing his son from going to Fajr prayer in the mosque due to safety concerns, and what is the correct course of action regarding that?

If your father's fear is justified due to insecurity or the prevalence of criminals, then obey him and pray Fajr at home with your parents, and you will receive the reward of congregational prayer. However, if his fear is unjustified, try to convince him to go with you to the mosque, or pray at home with him if he insists on preventing you, and obeying him is obligatory. You are not permitted to file a complaint against him, as this is an act of disobedience to parents.