What is the ruling concerning a father who uttered words several years ago that could be considered disbelief (kufr) or apostasy (riddah), among which was defending the utterer of a poetic verse that involves grave worship, approving a statement that there is no need for "Qul" (Say) in Surat Al-Ikhlas, and casting doubt on a Quranic verse, knowing that he maintains his prayers and recitation of the Quran? Is he excused by his ignorance? And does appointing the father as a proxy for the marriage contract after these incidents affect the validity of the contract? And what about obsessive doubts regarding the nullifiers of Islam?

The lyrics of the song mentioned are polytheistic (shirk), but your father's disbelief (kufr) is not to be judged based solely on what was mentioned until the matter is clarified to him and the misconception is removed. The judgment of disbelief is not a trivial matter. A Muslim is not deemed an apostate except for what the Quran and Sunnah have indicated to be major disbelief (kufr akbar) that expels one from the faith, or what the scholars have unanimously agreed upon, along with the fulfillment of the conditions for declaring someone a disbeliever and the absence of any impediments. Your father might have said the second phrase mockingly, and he does not become a disbeliever by denying something he does not know is from the Quran. The default assumption is the validity of your father's Islam, the validity of your marriage contract, and other such rulings. We warn you against succumbing to obsessive thoughts in this regard.