What is the ruling on working in a restaurant that belongs to a gas station which sells unlawful (haram) items, and is the wage received from the owner of the station, who states that he pays him from the restaurant's income, considered unlawful (haram)?

If the restaurant does not serve prohibited items, then working in it is not forbidden. The fact that the restaurant is owned by a company whose funds include the price or profit from selling alcohol does not make working in this restaurant forbidden; rather, it makes it disliked (makrooh). Thus, a person is rewarded for abstaining from it, but not sinful for doing it. This is because dealing with a person who possesses both lawful and unlawful wealth is not forbidden except in the case of the unlawful wealth itself. If their wealth is mixed without distinction, then it is disliked but not forbidden, according to the preponderant opinion.