Hi Nis20,
If you could potentially take your Official GMAT as late as late-November, then that is something to consider (as that additional study time - if used correctly - could put you in a much better position to hit your Score Goal). You would likely need to work on your applications while you're still studying - and while that might not be an ideal situation, there are considerably worse situations (such as not having a competitive-enough GMAT Score for the Programs that you plan to apply to and missing the deadlines entirely).
Statistically-speaking, raising a 600 to the point that you can consistently score 670+ will likely require that you commit to at least another 1.5 months of consistent, guided study (with a 700+ likely requiring more time than that) - and you would have to make significant improvements to how you handle BOTH the Quant and Verbal sections. Thankfully, the GMAT is a consistent, predictable Exam so you CAN train to score at a higher level. If you can accommodate that longer study timeframe, then there is a specific Study Plan that I could recommend that you follow.
GMAT assassins aren't born, they're made,
Rich