Should a son travel with his father who insists on traveling to commit sins and forbidden acts, or should he let him travel alone, and how should he deal with his father's stubbornness?

It is not permissible for you to accompany your father on this trip if you are certain of his intention, and it is not permissible for you to assist him in it. If you are able to prevent him by any means (including involving the authorities), then that is your duty. If you despair of preventing him, then your duty is to leave him and not accompany him, for the Prophet, peace and blessings be upon him, said: "There is no obedience to a creature in disobedience to the Creator."