Does using a respiratory device (oxygen) affect the validity of fasting?
Using an oxygen device does not affect the validity of fasting because oxygen is a gas with no physical substance.
However, if medicinal substances with physical particles are added to the oxygen, its use would break the fast, as it enters the body cavity through a natural passage.
What is the ruling on entering the toilet with something containing the remembrance of Allah?
It is disliked to bring into the toilet anything containing a reminder of Allah, such as the Quran or a sacred name (like the name of Allah, Muhammad, etc.). If one does that, etiquette dictates that he conceal it so it is not visible while entering the toilet, either by cupping his hands over it, putting it in his pocket, or inside his shirt if it is a necklace or ring. And Allah the Almighty knows best.
What is the ruling on preparing food for someone who is not fasting in Ramadan?
It is forbidden to prepare food for someone who is breaking their fast without a valid excuse in Ramadan.
Doing so would be assisting in sin, and assisting in sin is itself a sin.
Allah says {what means}: "but help ye not one another in sin and rancour" [Al-Mai`dah/2]
My father has debts and asked me to repay them years ago, and I promised him I would do so upon his death — is it permissible for me to go back on my promise given that I am unable to repay them, especially since he refuses to contribute to repayment on the grounds that the debt has become my responsibility by virtue of my promise?
All praise is due to Allah, and peace and blessings be upon our master the Messenger of Allah ﷺ.
The established principle is that a father's debt is to be repaid from his own wealth, if he possesses sufficient means. As for the promise made by the son to repay it on his father's behalf, fulfilling such a promise is strongly recommended, and breaking it is considerably disliked. Shaykh al-Islām Imām al-Nawawī, may Allah have mercy upon him, states: "Fulfilling a promise is emphatically recommended, and breaking it is severely disliked. The evidences for this from the Qurʾān and the Sunnah are well known." [Rawḍat al-Ṭālibīn,Vol. 2/P.278] Shaykh al-Islām Imām Zakariyyā al-Anṣārī, may Allah have mercy upon him, further states: "The reason fulfilling a promise is not obligatory and breaking it is not forbidden is that a promise is in the nature of a gift, and a gift does not become binding except upon receipt." [Asnā al-Maṭālib fī Sharḥ Rawḍ al-Ṭālib,Vol. 2/P.487]
Given that the son does not possess the financial means to fulfil his promise to his father, breaking this promise falls beyond his capacity — and Allah does not burden a soul beyond what it can bear. Since the father himself possesses sufficient wealth to settle his own debt, repayment must be made from his own funds. Should he pass away before doing so, the debt is to be settled from his estate. And Allah the Almighty knows best.
