What is the ruling on studying in secondary school and university, given the existence of subjects that are not beneficial for the required specialization, waste time and money, and are not financially necessary due to the availability of alternatives, while the parents desire the completion of studies?

Studying in secondary and university stages and striving therein is مطلوب (required/demanded) and carries a great reward if the intention is pure and the aim is good. It also involves obedience to parents and making good use of time. The intention behind studying to earn money and marry is not forbidden by Sharia. Some academic subjects indirectly benefit one's specialization or aim to broaden horizons and sharpen the mind.

As for describing one's father as an apostate, this is a heinous statement and a hazardous undertaking. Judging a Muslim to be an apostate is not a trivial matter; it only occurs when conditions are met and impediments are absent. This accusation might stem from whispers (waswas), so one must be cautious of them.