Was the girl's father justified in canceling the engagement due to his feelings of fear and distress, and is it permissible to try and convince him to reverse his decision, and how can he be responded to?

We do not know the reason for his withdrawal from the engagement and its annulment. If he had a valid reason, then there is no blame on him. However, you can approach him and try to convince him to reverse his decision and complete the marriage, especially if the girl is of good character and religious.