Legal Question in Business Law in Washington

There is not a practical legal answer to this question. You are legally entitled to be repaid, but bringing a legal action against your employer will likely create more problems than it will resolve. Suing your employer never enhances your career, costs money, and I can guarantee that future employers will not get an accurate retelling if they call him for a reference.

Practical suggestion (legal, but not based on the law). Bring to work no credit cards and no more cash than you need to get through the day and get home. When he sends you somewhere, explain "apologetically" that he needs to give you the cash needed before you go because you have nothing with you and are not in a position to adviance these funds. If he actually has the nerve to say, "In future you need to bring enough cash with you to make these shopping trips", you will have to confront him (respectfully) and say that you simply do not make enough money to be financing his purchasing, and since he does not ever pay you back, you will not advance funds for him any more. This may result in a very negative reaction, of course, but no more negative than if you brought a legal action against him. Furthermore, one sign that a restaurant is getting ready to go out of business is that the vendors are no longer delivering supplies, and the restaurant is buying supplies retail. If he is buying supplies retail AND sponging off his employees to do it, this restaurant may be in its final days anyway.