What should I do to return the illicit money that I am doubtful about, and how do I respond to my friend's prayer against me and my daughter with evil, knowing that I have repented from this money?

If a person is truly demanding a right of theirs and has been denied it, then it must be given to them. There is concern for the debtor regarding the supplication of the oppressed. Nevertheless, it is hoped that their supplication against the daughter will not be answered if it involves transgression or injustice, for Allah does not answer a supplication that entails sin or the cutting off of kinship ties.