So, I'll be honest here. I am being judgemental here but looking at the limited sentence construction in your posts above, I am sure you can score much higher than V29. I was in your shoes not too long ago. Here's what I would recommend you do:
(i) Take the course on GMATPrepNow dot com. Highly recommend it, helped me get from 710 to 760. Plus its cheap!
(ii) Attempt the entire OG and it'a supplements (quant review and verbal review). Review the incorrect questions to see WHY you attempted them wrong - i.e. wrong formula, guess, short on time etc. Doesn't have to be an elaborate tracker though.
(iii) Take the GMATClub Quant Tests. They will really help you lose your anxiety by making you comfortable with the format. You will also be able to see through what seem to be very tough questions after 8-10 tests. Review each test on the same day you attempt them. Helped me go from Q48>Q50.
After you're done with all of the above. Do the following:
(iv) Take the official GMAC CATs. 2 are free (which you've taken so ignore them) and 4 are paid. Spread the four across and don't attempt on consecutive days (at least a day between each, but possibly 2-3).
After you do the above, do the following:
(v) No questions / tests for 2 days before the exam. Light revision and then just chill, get a drink, watch a movie, whatever makes you not-anxious.
(vi) On the test day, do some light reading in the morning (newspaper?). It ensures your mind isn't asleep when you hit your first question in the test.
Other than this find which centre is the best in your city, as that has a MAJOR impact. I am in Delhi and hated the Pearson Vue centre in Yusuf Sarai. The Ansal Uni one on my third attempt was much more peaceful and relaxed.
Now all of this might not sound like a plan for 15 days. But ISB and NTU have some of the most competitive selection rates. So I would suggest don't burn another $250. Take a couple of months to do this peacefully and kill it.
I am a fellow Indian and struggled with the GMAT for 3 years. Feel free to PM if you've questions

Good Luck!