Hi Ana,
Many Test Takers spend 3 months (or more) of consistent study time before they hit their 'peak' scores. You have studied for a little over 1 month - and you now have less than 3 weeks before your Official Test Date. This is meant to say that if you want to score a lot higher, then you will almost certainly need more study time than you have allotted.
From what you describe, your overall plans appear to revolve around the goal that you want to receive word about whether you've gotten into School or not BEFORE Christmas. You might want to consider if that goal is more important than the goal of getting into your first-choice School (and if applying for Round 2 might better improve your chances of getting in). In addition, would earning the 'minimum score' that you referenced guarantee you admission into those Programs (and how do you know that for sure?) or that minimum necessary just to apply?
Regardless of how you choose to study going forward, you do NOT need to correctly answer ANY of the really hard/weird questions to score 600+, but you have to keep the little mistakes to a minimum. "Review" is an exceptionally important part of the GMAT training process; your ability to define WHY you're getting questions wrong is essential to defining the areas that you need to work on (and the specific things that you need to 'fix'). As such, I'd like to know a bit more about your last CAT. While a full Mistake Tracker would provide a lot more information, there are some basic questions that you should be able to answer (and the more EXACT you can be with your answers, the better):
After reviewing each section of this recent CAT, how many questions did you get wrong....
1) Because of a silly/little mistake?
2) Because there was some math/verbal that you just could not remember how to do?
3) Because the question was too hard?
4) Because you were low on time and had to guess?
5) How many Verbal questions did you 'narrow down to 2 choices' but still get wrong?
GMAT assassins aren't born, they're made,
Rich