I'd definitely do option 1 if I were you. It seem like a valuable once-in-a-life-time-life-enhancing experience.
You seem to have strong credentials as a med school applicant. Another thing you need to ask yourself is what you really want to get from this 1.5 year before med school. In my opinion a masters that cost extra bucks is not really worth it if your ultimate goal is med school. What you really want is experience that broadens your horizon and offer you a more comprehensive perspective in this world...blah blah blah.
I once considered apply to BU's MAMS too but, if you are going to med school any way, you'll eventually learn the same thing any way.
