Doing the Manhattan GMAT Advanced Quant

Hi. So, yesterday I finished the Manhattan Advanced Quant book. It took me ten days to go through its theory as well as the exercises at the end of the book (150 questions). I'd say that it's an excellent book. It does give you a set of tools that could help you in seeing questions in a different way, and just be more diversified in your methods of answering Quantitative questions, especially the harder ones. Also, it was very comprehensible in its explanations and lessons. Another good thing about it is the fact that it gets straight to the point, assuming that the reader has already mastered quant concepts to a certain level of proficiency. That was probably the only reason why I could finish this 400-pager in ten days.

When did I feel that I should get my hands on this book?

Well, I'm an average student when it comes to mathematics. My friends and family think that I'm some mathematical genius, but, to be honest, that has less to do with my mathematical prowess than their fear of mathematics (and hence, their being not so good at it) . I know what a mathematical genius looks like, and I most certainly do not consider myself to be one of that kind. To be sure, I've been preparing for GMAT quant for the last five months and only recently did I begin to see improvements in my quant scores. Before buying this book, I scored a Q46 (Kaplan Free Mock) and a Q45 (Economist Free Mock), and generally felt better at most of the questions I was being exposed to. In addition, I felt like diversifying my strategies in order to push my score closer to Q50ish level, and that was when I decided to get the Manhattan Advanced Quant.

What are my queries?

I'm here to listen to those who have also covered this book in its entirety. The reason is that I have certain queries that, if answered, would help not just me but also many who will tread this path in the future, with big dreams of acing the Quant section while remembering how difficult it seemed when they set out for preparing it. Cutting to the chase, here are the few questions that have surfaced while I was at it:

1. While I solved the questions (150, in all) at the end of the book, it seemed that most of the questions were not designed to be done within two minutes. It might just be me, but on average I took like 5 minutes in solving these questions. Now, of course, it's deemed to be a cardinal sin to spend more than 3 minutes on any given question, if need be, and the fact that I was taking 5 minutes has perturbed me to my core: "What if such questions pop up on the exam day, and I end up giving 5 minutes to them?"
So, could any kind expert share their understanding of these back-end questions and give their word on whether these 150 questions are especially designed to take this long, or was it just my being too clumsy? A better understanding of the average time it has taken the former doers of these questions could help set a benchmark for the coming lot.

2. Secondly, on average, I answered 6 out of every 10 questions right. Sure, I did very well on some exercises (9/10 or 8/10) but on others I was just pathetic (4/10, anyone?! ) Now, I'm wondering whether this is normal or were the folks who have done these questions were acing them all along? Simply put, I want to humbly see where I stand among the comity of the quant experts, who, by the way, have my heartfelt appreciation.
If I come to know I was below average in terms of accuracy, I'll then be able to figure out the reasons that held me back, and again that would also serve as a reference point for many.

I haven't taken a mock yet but I'll report back whenever I do to share in detail how this book helped me.

Thanks. I look forward to hearing from respected experts.