What is the ruling on the action taken by the questioner, who agreed with his father to cover his university study expenses in exchange for waiving his future marriage expenses, with the amount to be paid back as a debt? And does anything become due upon him now that he is in his second year of university, knowing that he suffers from severe obsessive-compulsive disorder regarding financial transactions?

If you promised to repay what your father spent on your education, then that is considered a debt upon you that must be repaid, unless your father absolves you from it. It is permissible for a father to earmark one of his children for financial support for a valid reason, such as their need for marriage or education. There is no harm in that, and he is not obligated to give the others the same, as long as the earmarking is for a valid reason. The marriage expenses that your father spent on your brother are not considered a debt owed by him to you. It is advised to disregard obsessive thoughts.