Just the one. His homebase monologue prompted Dave to pipe in, “You don’t really need me to be here,” to which Mason replied, “No, I don’t.” Dave would use later use that line on other comics in identical situations.
Don’t know for sure. Maybe JM didn’t feel the need to reappear. There was very little interaction; Jackie had a set to perform, and damned if he was going to deviate and have an actual conversation.