GMAT Prep Strategy Advice

Hello.
I have my GMAT on 22nd Sept-exactly 20 days from now and i gave my first full length mock a week ago. I gave an MGMAT mock a week back and scored a 600.(Q36 V36)I have a few questions as I'm in the middle of the reviewing process. I'm targeting a score of 720-730.

1)Regarding the individual sections, I've been practicing the Verbal section a lot more than the Quant section(with timer limitations) and so was able to complete the verbal section in time.
However, I ended up guessing around 12-13 questions(ridiculous I know) on the Quant section towards the end i was pressed for time. I had no practice of timing myself while doing Quant and thus i ended up doing so badly. Yet, i got a 600. My question is should i be worried?

2)Any particular strategy that i can follow so that I'm able to do Quant better and faster?

3) It's just my first mock and i plan to give a minimum of 10. How well do MGMAT mocks predict the actual GMAT score?

To add to it all I have another MGMAT mock and the Veritas free mock since the first MGMAT one. I scored a 550 and 600 respectively. So as you can see I’m stagnating around this score. I know Quant is my weakness so if you could guide me as to how to get better at Quant it would be great. Another weakness of mine and the one that pulls my Verbal down even though my RC is 70% accurate and SC is more than 85% is critical reasoning. So I’d like any expert's advice on that too. (Bunuel if you could help me with Quant it'd be great as I've read your GMATCLub Book for reviewing concepts).