9 weeks of studying, scored lower

Have you taken a GMATPrep test yet? I'd only trust GMATPrep as an indicator of your likely GMAT score; it's the only complete computer-adaptive test that contains real (retired) GMAT questions and that uses the real scoring algorithm. There's discussion elsewhere on this forum about individual companies' tests, but no company test can possibly produce scores as accurate as GMATPrep, and since the questions on company tests are company-designed, they may have idiosyncrasies which make them unrealistic- the math questions may be overly time consuming for example. From your experience, it seems that time pressure was an issue, but you should really take a GMATPrep test to see if it's still likely to be an issue on the real thing.

There is also going to be some natural fluctuation in your scores from test to test. For example, just by random luck, on some tests your guesses will work out well, and on some tests they'll work out badly. On the real GMAT, for example, the standard error is 30 points, which means that one third of the time, the test score you get will be more than 30 points off from your 'true GMAT ability'. So while the score you get on a GMATPrep or real GMAT test is likely to be fairly close to your ability, it's much easier to gauge your ability level after two or more tests; with one test, it's hard to know how much the score might have been affected by bad or good luck, but with more than one test, the luck is likely to cancel out.

My recommendations would be:

-don't 'call it a day'! You've come this far- you should see it through. Your current practice test scores aren't bad at all, and are acceptable at many MBA programs, and even with a 650+ you'd have a chance at the top programs;

-use GMATPrep to diagnose your current level, and if you haven't yet done so, work through as many real retired GMAT questions as you can find. They'll give you the best idea of what's on the test;

-diagnose your weaknesses as you go, and address them- figure out why you answer a question incorrectly, and make sure you'll get a similar question right the next time you see one. Anyway, lots of advice on this forum about that.

Good luck.