Hi anothermillenial,
If this is the only practice CAT that you've taken over the last 6 months, we don't have much of a basis for comparison right now - and your actual 'ability level' might be higher or lower than this Score implies. Raising a 670 to a 740+ will likely require at least another 1.5 - 2 months of consistent, guided study - and you'll have to make significant improvements to how you handle the Quant section. Thankfully, the GMAT is a consistent, predictable Exam, so you CAN train to score at a higher level.
All things considered, it's unlikely that you would "forget" anything that you've learned during your studies when you take that 2-week vacation in August (and from what you describe, you likely need some time away from your studies). It would probably be a good idea to plan for a little 'review time' once you return from that vacation though.
Based on your analysis of this CAT, you seem to understand that you made some silly mistakes, but it's not clear whether there are any other significant issues with your performance or not. "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 this 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