I don't know what to tell you. Whether the University admits it or not (they may be more interested in protecting the relationship that provides off-campus housing for other students than in your situation), you probably have tenant rights -- you've been performing labor in exchange for lodging, which is effectively rent. As a matter of fact, it may not be a type of rent that the owner wants to draw attention to because I'm confident that they aren't paying any taxes on the value of those services as income (you're a part of the "underground economy").

However, you'll likely need their reference to rent another place, so you have to balance that knowledge against how much you want to fight. You could investigate your rights through your sheriff's office, but if you make the owner go through an eviction process to stretch out your time, then they'll probably say that if/when they give a housing reference. Perhaps, after calming down a bit and getting more information about your rights, you might try to negotiate a small extension to avoid problems for either of you. I would STRONGLY advise against taking any action against the owners or their property that could provide grounds for legal action against you -- the short-term gratification won't be worth the long-term consequences.