What is the meaning of the Hadith: "Every body that is nourished by unlawful means, the Fire is more befitting for it," and does this include children and the wife if the father's money was unlawful, and is the daughter's Hajj accepted if it was performed with her father's unlawful money?

If your father takes usurious loans, he is sinful, and he should be advised to abandon that. As for the borrowed money, it becomes his property, and the حرمة (prohibition) is related to the act of borrowing, not to the money itself. Therefore, there is no sin upon you in benefiting from it, including performing Hajj with it. And if he deposits his money in the bank to take interest, there is also no sin upon you in eating from his mixed wealth. The Hadith which indicates that every flesh nurtured by unlawful means, the Fire is more deserving of it, is authentic and means that the one who consumes unlawful wealth is threatened with torment.