Hi vb27,
Many Test Takers spend 3 months (or more) on their studies before they hit their 'peak' scores, so it's likely that you just haven't put in enough time and effort yet. While another 3 weeks of study has the potential to help you a great deal, it's still not very much time.
Application deadlines are defined by each individual School/Program. In general, Round 2 deadlines tend to be in December and January, but you really should research the specific dates for the Schools that you're interested in (so you can be sure that your'e planning out your schedule accordingly).
Without know more details about how you've studied (and your Quant and Verbal Scaled Scores on your CATs), I'm not sure whether you've given yourself enough time to hit your score goals or not. However, if your goal is 700+, then 3 weeks is probably not enough time for you to make the necessary adjustments to how you deal with the GMAT. Pushing back your Test Date is one of the things to consider when dealing with the immediate goal: earning a competitive GMAT score. If your score isn't competitive, then the application deadlines won't matter.
GMAT assassins aren't born, they're made,
Rich