Regarding your statements on graduate work, I have to say, that makes it a LOT more appealing! :) From what you said about doing the graduate work only because you want to, it sounds like your heart and motivation are in the right place. Without doubt, earning a graduate degree gives you several notches in the life experience meter versus someone freshly out of undergrad.
This one I'm not sure about either way. UBC isn't biased towards selecting for science majors. Conversely, I don't think they deliberately look for non-science majors. I really believe that as long as your GPA and MCAT scores fall above the set thresholds, your application is dependant on personal characteristics.