For each of these cases which is the designation that best describes my role in class
Teaching Fellow (which is a title usually reserved for an instructor who is also otherwise affiliated with the institution as a student, usually graduate), alternatively, I have seen a few graduate students who taught classes in their own right and were given the title of Lecturer, which is analogue to "adjunct" at some institutions--generally, though, even at institutions that use the title "adjunct" and not "lecturer" for their adjunct professors, graduate students who teach courses in their own right will usually still be referred to as a "lecturer". The reverse, as far as I know, is not true though--at institutions that use "lecturer" over "adjunct" or where both "adjunct" and "lecturer" are in use, students that teach are not called adjuncts, but are usually identified as "instructor" or, though rarely, "moderators", or even, the difficult-to-cv pseudo title of "Course led by...".
Teaching Assistant. Your overview might literally be the definition of a teaching assistant.
Monitor. Proctor. Or, more specifically, Lab Assistant or Lab TA.