Very specific query: How to master technique of applying concepts

Hi All,

It has been 3 months since I have been studying for GMAT regularly. I have gone through following material for various sections:
Quant: Expert's Global Study Kit, gmatclub Math book for select topics such as Number systems/Geometry etc, Number systems from Manhattan.
Verbal: Expert's Global Study Kit for entire verbal section, Sentence Correction Grail by Aristotle, CR Bible, Gin's RC technique, All of Manhattan's material on SC.

I have given practice tests of Expert's Global & am stuck at an average score of 630-640 (Q44, V33). The highest score I got was 690 (Q 48, V 36).
I have done some analysis of my weak areas & have found out that my ability to apply concepts & get the question right is inversely proportional to the difficulty level of the question e.g. I consistently struggle to apply concepts of geometry say circles/triangles/squares etc to questions beyond 700 point difficulty. Funny part is that when I look at the answers & explanations to such difficult questions, I feel that I could have never thought of cracking it that way!

When it comes to verbal, again I am able to crack SC questions of <650 difficulty level with 90% accuracy & CR @ 80% accuracy. With RC main point of struggle is time management. I have tried everything from mind mapping to short notes to what not (practiced >50-60 RCs) & have not been able to either manage para & questions within average time of 2 minutes / question or get an accuracy in high 90%. My average accuracy with RC paras of decent difficulty has been 70%.
I am keen to understand how can I learn how to apply concepts in an efficient manner to different question types as so far trying to grasp the technique of doing so has proven futile as each GMAT question is different from the other! Even if I create some kind of log book of how a particular difficult question type was solved, I find out that the next difficult one of the same type had a very different approach!

I am not keen to take my prep beyond the month of December as I have already spent some time & have started to feel fatigued. My aim is to score anywhere beyond 700 as I am an Indian non IT male (Consumer Healthcare Marketing) & am well aware that if I score <700 my chances of even getting shortlisted by top ranked schools will dwindle.
Looking forward to some tips / tricks from this wonderful community so that I can get rid of this weakness & ace the GMAT.