Write good essays and you'll be moderately surprised come March next year

Only thing that'll hurt you is the lack of humanities, but it probably wouldn't matter too much.
I personally wouldn't bother taking the Phys SAT II...MIT has publicly stated not to retake anything if it's over 700, and your Chem/Bio scores are good enough. (For the record, I got a 750/780 Chem/Phys respectively, and I don't think they even recorded the Chem score).
I'll second ElderCookies about your "specialties".