GMAT Strategy

After several months of studying i'm still hovering around the 600 level on practice tests. I've scored as high as 640 and as low as 530. I have a scheduled GMAT appointment April 17th, and would love some advice to help me get over the hump and closer to 700 before that date. I've scored average on quant and below average on verbal. My last practice test was 590: 41 quant and 30 Verbal (MGMAT test). Verbal is defiantly my weakness, although I need to improve my quant score as well. I've taken the official practice tests a couple times and scored 640 the last time I took one of those. I have never finish the Quant section on time and usually end up guessing on the last 6-7 questions. I've sat for the GMAT twice; 1st time I scored 530 and the 2nd time canceled my score after a frustrating testing experience. I struggle with test anxiety (like everyone else), often get distracted and read things over and over during the test.

Any ideas on how I should spend my final 2 weeks of prep? Is it realistic to improve 50 points over 2 weeks? I really want to get 700, but need to get above 630. Should I wait to take the GMAT until my scores are more consistent and on par with where I want to be? Lastly, if I take the GMAT this third time on the 17th and get just an average score, is it going to hurt me significantly to take the test again with 2 reported scores and 1 canceled score already? I've heard its ok to take the test twice and even three times, but four might be stretching it.

I've submitted an application with my low GMAT score to a school that is waiting for me to post a higher score. I would prefer to take the GMAT as soon as possible (17th), but I don't want to put my future in jeopardy with 2 average/low scores and a canceled score. Perhaps I need to move it back. I would appreciate any advice! Thanks in advance.