I teach math at a state university too, but as a grad student. I can sometimes get into the zone where I stutter less while teaching, but it varies from day to day. I'm sure this is true in other disciplines too, but I notice that when explaining mathematical concepts there is not a lot of room for word substitution; in fact, looking for ways to substitute can get me into trouble because I need to convey the subtlety of various definitions. Plus there is just no good synonym for derivative (unfortunately!). Good luck with your continued job search. By the time you get to the 91st interview you are (probably) pretty used to stuttering during interviews. At least this is what I tell myself, to prepare for being in the same boat. Best wishes!