What is the ruling on leaving a job at a hotel that sells alcohol, pork, and offers massages, and instead working as a teacher for a lower salary, given that the father is not in favor of this?

Working in a hotel that sells prohibited items is unlawful (haram). If your work there involves what is impermissible, then it is not permissible to continue in it. You have done well in leaving this prohibited work and turning to teaching, because repentance is not complete except by abandoning the sin with the resolve not to return to it and remorse for it. It is unlawful for you to obey your father in returning to the prohibited work, for there is no obedience to a creature in disobedience to the Creator. However, you should be gentle with him and explain to him the reason for your leaving the work, and make it clear to him that worldly wealth cannot compare to Allah's wrath and punishment.