GMAT Strategy

I gave my first GMAT practice test on Saturday and scored 550. This score was after 2 week long (3-4 hours on weekday & 8 hours on weekends) studies of familiarizing with the GMAT questions and solving quiet a few without actually learning anything new. I consider myself very decent in Quant (except probability) but extremely weak in Verbal.

After I reviewed my quant wrong answers, I found that I did a lot of careless mistakes in selecting the answers and selecting an answer without analyzing other options. Verbal has never been my strongest link. I usually select what feels right at that time. If I do the same question after sometime, I will probably pick a different answer. I did worst in sentence correction. I'm very interested in learning basics of verbal and starting again. If anyone has any suggestion that can help me out that will be great. Or the best book that can give me a refresher of the verbal basics.

Time management was another big issue. I know that I can solve almost all of the quant questions in about 5-6 minutes but obviously that's not going to help in the exam. That's why I quickly picked answers without actually solving them. As a result, I finished both quant and verbal about 7-9 minutes before the actual time (and hence the low score).

Currently, I have: OG13 with both guides, Kaplan Premier book, Kaplan course book with pocket reference. Do I have enough or do I need more books to practice from? Should I buy MGMAT strategy guides?

I am scheduled to give the exam in mid-September and I believe I learn more when I study myself. That's the reason I'm not opting to take any prep courses. I can spend 4-5 hours everyday and 12-14 hours over the weekend. I am willing to work super hard to get a decent score.

Couple of questions:
1) Do I need to buy more study material?
2) What might be the best book/place for the verbal refresher?
3) Has anyone scored above 700 without any prep course?
4) Are the techniques taught by prep courses very useful and better than actually solving the questions? For quant and for verbal?
5) Given the information above, should I start with solidifying my quant score and finish that first and then take on verbal? Or verbal first then Quant? or both together?
6) Should I worry about time right now or should I focus more on solving the question while solving OG13 questions?

Thanks a lot!