Is the wife entitled to know every detail of her husband's additional income, savings, and debts? And is she allowed to cause problems if the husband refuses to disclose this, even though he is not negligent in household expenses?

The husband is not obligated to inform his wife of all his properties, savings, and financial transactions, unless doing so would lead to the neglect of her rights. If the husband spends on his wife according to what is customary, then there is no blame upon him for concealing some of his money from her. If the wife uses this as a pretext to neglect her husband's rights, then she is unjust. The husband is advised to treat his wife kindly and to deal with her with wisdom and gentleness.