GMAT Study Plan Help Moving from 620 (Q44, V31) to 750

Background
The first time I studied for the GMAT was during the summer of 2011. I just used the Official Guide as my main resource for practicing questions. Halfway during my study, I found GMATClub, but did not take full advantage of its resources. Foolishly, the first time I took a GMATPrep practice exam was the week before my exam date. I took the actual exam in September 2011 in the afternoon after a night of 6 hours of sleep and scored a 620 (Q44, V31).

2 years later, I am back, and I am aiming for a 750 (Q49+, V42) with a goal of taking the exam in May 2014. My weakness is in Verbal especially in CR, and my strength is in Quant. I am a native English speaker, and I am a working professional.

I started my studying in October 2013, and I planned to take the exam in March. However, I quickly realized that after 2 months of studying Quant, I would not achieve my goal, so I pushed the date to April. Unfortunately at this time, I am only getting 40% of 600-level Quant questions correct, and only 30% of 600-level GMATPrep questions. I also need to start studying for RC and CR. Because of this, I pushed the exam again to May 2014.

Material
Quant
PS - Magoosh
DS - Magoosh

Verbal
SC - Magoosh, MGMAT; classic books (Animal Farm, The Great Gatsby, Moby Dick, etc.) and articles from WSJ, Bloomberg, NYTimes, Atlantic
CR - MGMAT
RC - MGMAT, Magoosh; classic books and articles

Strategy
My strategy is to review the fundamentals of all question types before practicing questions. I checked the question types that I missed the most in my past exams, and focused my practice on those. I then practice questions on this site from reliable sources (GMATPrep, OG, Veritas, MGMAT, etc.). I keep an Error Log of these questions, and for SC, I try to understand why the correct answer is correct and why the incorrect answers are incorrect. In Quant, I try to find the quickest solution to the problem, and I have recently decided to stop working on Quant problems that take me longer than 3 minutes to solve, because it means that I am approaching them ineffectively. Right now, I would like to give a special shout out to Bunuel, VeritasPrepKarishma, and walker; your help has been invaluable to my studying.

Starting in November, I committed to about 5 Quant questions and 5 SC questions each workday (M-Thursday) and 5 Quant and 10 SC questions each weekend day (F-Sunday). The number is low, because I thoroughly review each question to ensure that I understand the underlying concepts. Ex: It takes me about 1 hour to review 5-6 SC questions, and I believe the review time per question needs to significantly decrease.

At the beginning of November, I took one free Quant exam on this site and scored a measly Q41, and I took one of the GMAT club tests on 12/28/13 and scored a Q35, which was worse than I had scored in the first exam. Most of the reason for scoring low on the most recent exam is that I spent too much time on each question (2m 30s+, 3m+, 4m+, and even 5m+).

Please tell me what you see me doing incorrectly, because I have not seen a lot of score improvement since the first time I started studying, and I definitely know that something needs to change in my study plan in order for me to reach my goal.