Is avoiding the mother who creates problems over money, and dealing with her only when necessary for fear of her injustice and curses, considered dutifulness towards her? And is the prayer of an oppressed father answered? And is the prayer of an oppressive mother answered?

The supplication of an oppressive mother against her children is not answered, whereas the supplication of an oppressed father is answered. The mother and sister must repent to Allah for what they have done to the father. You should gently remind them of the necessity of repentance and explain that a mother's supplication against her children, her striking them, and harming them for the sake of money is not permissible, and that the sister should not seek to harm you. If they do not respond to advice, there is no sin upon you if you distance yourselves from the harm, while being careful to show filial piety to the mother, obey her, treat her kindly, avoid displeasing her, and ask Allah for her guidance.