Is the reason for the family's sustenance being withheld what the father does by killing animals under the pretext that they are jinn, and what is the solution for the father who refuses to sell the land and justifies his actions despite his religious commitment?

We have no definitive proof that the father is the cause of the deprivation of sustenance. Killing animals that Islamic law has not permitted killing is forbidden, except for those explicitly mentioned in the texts for killing, such as predatory animals and jet-black dogs. As for the jinn, they can take various forms, such as dogs, cats, snakes, and others, especially black ones, because blackness gathers demonic powers. The killing of frogs has been prohibited, and it is disliked to kill a harmful cat unless its harm cannot be repelled except by killing it, and that should be by slaughtering, not by torture.

For protection from jinn and devils, it is recommended to recite Surat Al-Baqarah, especially its last two verses, and Ayatul Kursi, and to recite Surat Al-Ikhlas and Al-Mu'awwidhatayn (Al-Falaq and An-Nas) three times in the morning and evening, and to maintain regular remembrance of Allah (dhikr).