1) No, the second year biomechanics is definitely not something to sweat over. The upper level ones can get a bit challenging, but the introductory biomechanics course is largely akin to an introductory physics course. You cover kinematics, dynamics, energy, momentum and collisions, etc. all of the major concepts you likely saw in grade 11.
What you may not have seen are the rotational analogues of these concepts. For instance, "moment of inertia" is the rotational analogue of "inertial mass", or something's tendency to resist accelerating. "Torque" is the rotational analogue of force. Something tricky that arises is the concept of equilibrium - In grade 11 an object would not accelerate if and only if all forces were equal and opposite. This is no longer true, as the torques may not be equal. (ie. if I push on both sides of a wrench with the same force, but in different locations, the one with the greater mechanical advantage will dominate and the wrench will still perform work).
However these concepts will likely be under-emphasized in 1L03 regardless...I would recommend taking your chances. The fact that you worked hard in grade 11 means you will likely do so again and not be caught off guard by biomechanics.
2) Not sure, sorry. No experience with residence life.
3) Yes this is true, but only for certain universities - in fact I know of one guy who applied to medical school and got in with a math degree. (He independently learned and aced the MCAT)
I would highly advise you do some research into the topic, namely which schools have relaxed pre-requisite courses. From my experience (a few years back), almost exclusively, all schools outside of Ontario have very rigid pre-requisite requirements (full year of bio with lab, orgo with lab, one english course, a stats course, etc.), while schools in Ontario are more relaxed and assess based on interpersonal skills, volunteer experience and so forth. See
http://www.ouac.on.ca/docs/omsas/b_omsas_e.pdf for Ontario Med School requirements.
Their philosophy is (according to McMaster, who is actually a pioneer in med school admissions), whatever science you don't know, you can always learn in the first year of medicine. What you can't learn however, is how to be a compassionate individual, with good ethical sense and problem solving ability. This is what is being assessed (fingers crossed) by McMaster's online assessment tool (CASPr) and in an interview.
