Does my wife's refusal of me necessitate that I hit her, meaning, is it considered an act of disloyalty (nushuz)?

Voluntary fasting is permissible, and the fasting person receives a great reward. It is authentically reported in Sahih Muslim, on the authority of Abu Hurairah (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: "The best fasting after Ramadan is Allah's month of Muharram, and the best prayer after the obligatory prayers is the night prayer."

If a Muslim intends to observe a voluntary fast on a specific day, then something prevents him from completing the fast, such as illness, travel, or an invitation to food, he is permitted to break his fast, and there is no sin upon him. He is not obligated to make up that day, though it is recommended for him to make up that day if it does not cause him hardship.

Imam An-Nawawi (may Allah have mercy on him) said in "Al-Majmoo' Sharh Al-Muhadhdhab": "If one intends to observe a voluntary fast and then breaks it, there is no make-up upon him according to us... whether he broke it with an excuse or without an excuse... This is the view of Malik, Abu Hanifa, Ahmad, and the majority of scholars."

It is narrated in the hadith reported by Imam Muslim from Aisha (may Allah be pleased with her) that she said: "One day the Messenger of Allah (peace and blessings be upon him) came to me and said: 'Do you have anything?' I said: 'No.' He said: 'Then I am fasting.' Then he came to us another day, and I said: 'O Messenger of Allah, we have been given Hais (a sweet dish).' He said: 'Show it to me, for I woke up fasting.' Then he ate."

The meaning is that the Prophet (peace and blessings be upon him) was observing a voluntary fast, then food was presented to him, and he broke his fast, and he did not make up that day. This is proof of the permissibility of breaking a voluntary fast and the absence of an obligation to make it up.

And Allah knows best.