Received a PM asking me to reply. Sorry for the delay; I've been on vacation.

First, nice job on your test. I know your goal is higher, but you still got a great score!

A few things:
1) this test is not scored based upon percentage correct; it's scored based upon the difficulty levels of the questions you're answering
2) everybody gets a lot of questions wrong; it doesn't really matter how good you get (the test will just give you something harder!)
3) the earlier questions are not worth more than the later questions - that's a myth. You have to maintain steady performance to the end of the test. The thing that kills your score is a string of questions wrong in a row - so if you, for example, spend extra time at the beginning and run out of time at the end and get 5 wrong in a row... your score will drop quite a bit.

If you want a 750, you MUST fix the timing; you will NOT get that score without having perfect timing. Notice that I do not say: you must get them all right. You won't get them all right. That's okay. What you need to do is get most right (maybe 30 or so out of 41) while not having strings of questions wrong in a row.

That requires you to recognize when you really just don't know - it's going to happen, because the test can always give you something harder - and then just let go before spending too much time. One rule I follow: when I've narrowed down to 2 choices on verbal, I look at each choice ONCE more and then I pick. Either I know or I have a good guess or I don't. Agonizing for a while between the two isn't going to improve my odds.

I think it would be a good idea for you to take a practice test that gives you data on your timing and the difficulty level of the questions - the GMATPrep tests don't do this but a lot of test prep company tests do (ours gives you this data, for example). That way you can see how much time you're spending, where you tend to spend too much time, etc. You can also see what the difficulty levels are. For instance, you had 5 SCs wrong, but maybe they were all 700+ questions, so that's not necessarily a weakness. Conversely, if some or most were sub-700, then you'd have to consider that a weakness (given your goal).

Next, you don't mention what you are using to study. Where are you learning the grammar rules? How are you learning what to do with the different kinds of CR and RC questions? Those things are difficult to learn on your own, just by doing practice problems. If you don't already have books that teach you how to do these verbal questions, you'll need to identify some good sources and buy them. Ask around here to see what people have used and liked. (I don't make specific recommendations because I'm obviously biased towards my own company! )