What is the ruling on dealing with the fiancé's father if it is highly probable that he practices charlatanism and sorcery in Ruqyah, especially concerning financial matters and living with him in a house built with an usurious loan, and are his actions inherited by his son?

It is not permissible to accuse anyone of sorcery and charlatanism except with clear proof, because accusing someone of sorcery is a serious matter. As for living in a house built with a usurious loan, there is no harm in it, despite the prohibition of borrowing with usury. However, the forbidden aspect is related to the borrower's liability, not to what the loan was used for. As for benefiting from mixed money (forbidden and permissible), there is no harm in accepting it and benefiting from it.