Every application is a story. What is your story? Include things that are relevant to the story. If you did research in medical school then I would also include college research. Similarly, if there is a clear theme to your volunteering that runs through college and medical school then maybe the college stuff is worth including. Gap year = college for the purposes of this discussion, it's either "medical school" or "prior to medical school." The description was mainly an elaboration of what I actually accomplished (titles don't mean much if you didn't actually do anything) although if there was a significant take away that naturally came to me I probably included it. Definitely didn't force anything.
For the misdemeanors, I would talk to your school about how to handle it. My gut says if they have been expunged that you should not include them but I don't know enough to answer confidently especially since you did have to document them on AMCAS.