Hi Nalgh,
I'm hoping that you can clarify something that you wrote. You stated that if you 'screw up' this attempt, then you'll be DONE applying for an MBA - why is that the case? Couldn't you just apply in the next application cycle?
I bring this up because your timeline/plan is not likely to be successful. Most Test Takers need 3 months of consistent study time to hit their respective "peak scores"; with your timeline and goal, you'd have to improve 210 points in just over a month. That is not likely to happen. I'm not saying that it's impossible, but it's not a realistic expectation.
While this probably does not make you happy, you have to remember the REAL goal. The MBA is what you're after - if you have to change your timeline a bit, then so be it - a goal this "big" doesn't always occur exactly when you want it to, but it doesn't have to 'disappear' either.
You can study as planned, and take the GMAT as planned, but you also have to think about putting together a better, more thorough plan. The MBA that you're after is valuable and requires that level of forward-planning and action.
GMAT assassins aren't born, they're made,
Rich