Is this fair treatment at work?

no! Everything else you just explained is completly legal, you may just ask your supervisor, im freelance, and technically self-employeed, why do i need to do your employee duties? And if he doesn't like it, either put up with it until something better comes along or find a new job! But honestly thats not uncommon, but you don't have to sweep or mop the entire office, isn't the kitch also the janitors job?