Is the father sinful for his anger at the driver who started the altercation, and is the son's plea for forgiveness for his father accepted?

If a father's outburst at a driver involves a sin, such as unjust cursing, then he is sinful. If it is justified and does not involve a sin, then there is no sin upon him. If the father wronged the driver, he should apologize and soothe his feelings. Your seeking forgiveness for your father is a good and righteous deed from which both you and he will benefit, for Allah commanded His Prophet, peace and blessings be upon him, to seek forgiveness for his sin and for the believing men and women. It is recorded that whoever seeks forgiveness for believing men and women will receive a good deed for every believing man and woman, and this is even more emphasized and fitting in the case of parents.