Your dream of the vampires sounds as if you are in real life surrounded by the wrong people. Even the teacher, represents a friend you trust more than the others, and he gave you bad advice in the dream.
It could be his advice was not only bad for ridding yourself of the wrong people. Or this person is putting these things in your head, that these people are not right for you. And his tool the banana, does not work, because the question is: "Are the vampires really the problem? or is that close friend the problem?" The family element can mean friends, who seem as family.

I would say its time to clean house, and get rid of friendships or relationships that are draining you, like a 'vampire would.'