What is the ruling on eating and drinking from the wealth of a father who works in the central bank and a mother who works in the tax authority, and is this wealth considered mixed such that it is permissible to eat from the half that is lawful therein?

You are not permitted to eat from your father's money earned from working in a usurious bank if you are able to do without it. Otherwise, it is permissible to the extent of necessity. Similarly, if the money is mixed and the unlawful portion predominates, then it is disliked to eat from it. As for the mother's work in taxes, it is permissible with certain controls. It is advisable to gently counsel the parents to seek another source of income.