Is the remaining amount from the salary earned at a store that sells gold on installment considered unlawful money, and is one sinful for spending it on their family, and if so, how can one dispose of it?

Selling gold for deferred payment is prohibited, and it is forbidden to work in a shop that does so. The salary from such work is unlawful, and one must repent. Any remaining money from it should not be used; instead, it should be disposed of by spending it on charitable causes, unless one is in dire need of it. As for the money that was spent previously, there is nothing required concerning it except repentance.