I'm sorry you had a disappointing text experience. I'll answer your 2nd question first: no, your chances are not hurt (assuming you do eventually get a score that's more in line with what top-10 schools want). The schools use your highest score, so as long as you do get the score eventually, you're fine.
I'm not going to answer your first question because it's not the right question to ask. :) There are no guidelines that say "everyone should do ABC to reach 700, and it will take everyone X amount of time." The only real answer is "you should do what you need to do based on your specific issues, it will take the time and effort that it takes, and that's when you'll take the test again."
So, your verbal score matched your practice but your quant score dropped. You also mentioned timing issues.
First, read this (right now):
https://www.manhattangmat.com/blog/inde ... lly-tests/Are you actually taking the test that way? Or are you still using the old school mindset, trying to get everything right? The vast majority of people who study and study but don't improve are still using the old school mindset.
Next, read this (right now):
http://www.manhattangmat.com/blog/index ... -the-gmat/Are you studying in this way? If not, time to start!
I'll give you some resources on time management below, but you'll also need to diagnose your strengths and weaknesses in general in order to come up with a study plan. Use the below to analyze your most recent MGMAT CAT(s):
http://www.manhattangmat.com/blog/index ... ice-tests/** Note whether you took those tests under 100% official conditions, including the essay and IR sections. If you skipped either or both of those sections, took longer breaks than allowed, used the pause button, or in any way took the test under non-official conditions, then your practice scores may have been artificially inflated. Take that into account in our analysis.
Figure out what you think you should do based on that analysis. Then come back here and tell us; we'll tell you whether we agree and advise you further. (Note: do share an analysis with us, not just the raw data. Part of getting better is developing your ability to analyze your results - figure out what they mean and what you think you should do about them!)
Take a look at these two articles on time management:
http://www.manhattangmat.com/blog/index ... -to-do-it/http://www.manhattangmat.com/blog/index ... nt-part-1/And start doing what they say!