Is the wife sinful if her husband's refusal to engage in marital relations is due to his resorting to masturbation when angry, despite her constant readiness to fulfill his conjugal right out of fear of God?

There is no sin upon you for your husband's forbidden masturbation as long as you do not refuse to obey him when he calls you to bed. However, if he does not call you, you are not obliged to offer yourself to him. Advise your husband to avoid this forbidden habit, and be keen to keep him chaste, and avoid causes of discord. And remember that among the good manners of a woman is her striving to please her husband, even if he is unjust, for the Prophet, peace and blessings be upon him, said: "Shall I not inform you about your women among the people of Paradise? The loving, the fertile, the one who returns to her husband, who, if she causes harm or is harmed, comes and takes her husband's hand, then says: 'By Allah, I shall not taste sleep until you are pleased.'"