First off, just calm down about the whole thing. You said that you were scoring 13's on the practice verbals, right? How were you doing on the practice science sections? Do you feel more confident than last time?
I managed to designate 3.5 straight months of time to nothing but MCAT prep and was able to increase my score by 10 points from my first attempt. The week before my second try, I was confident that I was going to do worse than my first attempt and started to lose my **** (in the same way that you are right now). I took some time off from studying, played lots of video games, watched movies and went out with friends. I essentially did everything I could to forget about the test for a few days before hand, then went into it thinking I was as prepared as mentally possible. Everything worked out fine.
It would be helpful to know: a) what the schools' stats are, and b) what your other stats are before dishing out advice. You have a very solid MCAT (make no mistake about that), so to not get an interview at your school of choice makes me suspect that there may have been some other discrepancy in your app (low writing score, middling GPA, lack of research, lack of clinical experience, who knows). In terms of re-applying, schools like to see improvement in whatever area was lacking.
My honest opinion is this: before re-taking, contact an admissions officer at McMaster and get some feedback. They should be able to tell you where your weaknesses (AND strengths) lie. Don't assume that your MCAT is the only thing holding you back. While it's an important part of the process, it is NOT the end-all, be-all.
But if you're set on re-taking, go for it. There's not much advice I would give someone who has already gotten a 35. A lot of applicants here would dream of getting such a score.
I also noticed that you took the MCAT last August. Could some of this simply be related to applying late in the cycle?