Hi kamrim322,
While you might be tempted to do a lot of studying during these last 3 days, you should NOT do anything too work-intensive. In these last few days, you should limit your studies to general practice and light review (NO CATs and NO 'cramming') - you would be better served by getting some extra rest so that you can go into Test Day calm, clear-headed and ready to work.
To score a 600+ on the Official GMAT, you do NOT need to correctly answer any questions that you think are too hard or too weird - but you have to keep the little mistakes to a minimum (especially on the 'gettable' questions). As such, you should be mentally prepared to 'dump' a few questions on Test Day (again, any prompts that YOU think are too hard or too weird; take a quick guess on those questions and move on).
As a bit of review, you might consider revisiting your last few CATs. Which questions did you get wrong because you made a little mistake (and what would you do differently to make sure that you don't make a similar mistake in the future?)? Which questions did you think were too difficult (and how much time could you have 'saved' if you had just dumped those questions instead?).
GMAT assassins aren't born, they're made,
Rich