Is it religiously obligatory to allocate one-sixth of the salary to the father, knowing that the salary is spent on the household and family and there is no other source of income for them? If that is obligatory, how is this one-sixth calculated based on the mentioned salary details?

We ask God to help you and grant you success in sponsoring your mother and sister, and to greatly reward you. Your father bears a great burden by abandoning his responsibility and mistreating his children, for the Prophet, peace and blessings be upon him, said: "There is no servant whom God has entrusted with a flock, and he does not surround it with his sincere advice, but he will not find the scent of Paradise," and he also said: "It is enough sin for a man to neglect those whom he supports." As for your duty towards your father, it is to be patient with his harshness, to maintain ties with him, to honor him, and to pray for his guidance, for he has the right of a parent even if he were a polytheist. He has no right to your salary except through kindness, and you are not obliged to give him from your money unless he is poor and in need of support, in which case you give him what suffices him.