theories can still have the option of being debunked, if it was totally unrefutable, it would be a law. yes there are facts other wise it would never have become a theory in the first place. i.e. continental drift theory vs plate tectonics
no offense and not to sound ignorant, but they are teaching gravity as a law in school. whether this is a misrepensentation of the truth, I don't know. Theory is a strict code of facts...like in music, however theory in music can sometimes be broken and rules can be bent because it is not law, which leads to people thinking outside the box.
In science, a theory is as proven as anything gets. In other words, nothing is ever known absolutely. That gravity exists is a fact, how it works though is a theory. The term "Law" is an antiquated term in the field of science and should be replaced with theory.