I'm sorry that you had a disappointing test experience.
As you mentioned, your quant score was about what it was on your later practice tests, but your verbal score dropped a lot.
One issue was almost certainly stamina. Taking only one full-length practice test (compared to 4 without essay and IR) is not enough. You were essentially used to being done with the test around the time that you had to start Verbal on the real test. (And there's a good chance that you worked harder on the essay and IR sections on the real test than the practice test - because you knew the real test counted and the practice test didn't. That would have just made you more tired during the Verbal section on the real test.)
Next, if you want to get to 680+, you will need to do quite a lot of work on the Verbal side of things. You mention that you have read some articles on the blog and that you did lots of OG questions. What materials did you use to actually learn grammar and learn how to tackle the different kinds of CR and RC questions?
It's very difficult to try to derive the lessons yourself just by doing OG problems or reading some articles. I recommend that you research the different prep books available for SC, CR, and RC -- and, when you find something you like, buy them. (I'm not explicitly recommending my company's books because of course I like our books.
It's better for you to research yourself and decide what you think would be best.)
Note: it can sometimes be difficult to find books in India - the shipping costs can be quite high. Lots of books now come in electronic form, so you don't have to have the physical books shipped to you. (And the e-books are often less expensive than the physical books!)
I do want to mention that your goal is to raise your score almost 200 points in 2 months. That is a very ambitious goal. Most people would not be able to achieve that kind of increase in that timeframe, particularly when most of the increase will need to come from just one section. (You're already at 46 in quant and the scoring only goes up to 51, so you don't have a lot of room for improvement in that section - though you will still want to work on math as well as verbal.)
I'm mentioning this because I think that it's best to plan for different scenarios. If you can't achieve that score increase in that timeframe, what would you prefer to do? Would you rather apply to some different schools with a lower score? Or would you rather postpone b-school for a year and continue to study for the GMAT? There isn't one right answer - it depends on what you want.
If you hadn't told me that you want to take it again in 2 months, this is what I would advise:
First, study from our Foundations of Verbal book, or something similar. This will help you to build your foundational skills across all areas. That will take 4 to 8 weeks, depending on how much time you have to study each day. During this time, also read good-quality material every day - the Wall Street Journal, the New York Times magazine, and good-quality books (including novels!).
Next, set up a self-study plan or join a course that teaches you the kind of material that's in our main SC, CR, and RC strategy guides - basically all of the grammar and meaning, as well as the different question types, that are tested on the GMAT. (Plus quant - as I said, you'll also want to improve quant.) That will be another ~2-3 months. (Also, note: I wouldn't recommend immediately starting this phase because a verbal score of 17-25 indicates some holes in your foundational knowledge that need to be addressed first.)
At that point, you may be ready to score 680-700* or you may need more review time. (*Note: there's no guarantee that anyone will ever hit a certain score, of course. I can't say for sure that following a particular path will definitely get someone to a certain score.)
If you still want to try to go for the mid-Oct timeframe, then you will need to accelerate this process without burning yourself out. That can be tough. Keep in mind that it is not always better to study more. Sometimes your brain needs a mental break.
What do you think about all of the above?