GMAT Verbal & Essays

I have gone thru OG13,MGMT SC book and other online materials for all the theories related to VA and QA.
I have taken 5 MGMT tests and have scored max 590 , mostly because of my low VA score and inconsistency in taking tests ( 1 test in 20 days, with no study in gaps).

My QA score is around 44. I need overall score of around 680.
My VA score has been fixed at 27. What can I do to improve score .
I am taking GMAT in next 45 days.

Now I don't want to go through any additional books ,as I am confident that I have come across all the fundas/ trip & tricks at-least once,only thing that I need is fine tuning my test taking strategy and lots of practice.
Please advice how can I improve my score from 590 to 680 (at least) in next 45 days,what should be my strategy now.
I can spend max 45 mins on weekdays and 4 hrs on Weekends.

Thanks