The challenge I see is the time of the year you're flying. I don't know the fare trends well enough and don't of tools to track trends in Indian domestic market but would hazard a guess that Dec 29th to Jan 8th seems to be peak period.

Look at checkfares right away rather than wait for later. Checkfares may get expensive closer to travel date and if you want flexibility to change for last minute changes I believe the 14 day passes are better.

I too recommend business class. The premium in fares over economy compared is much lower than the premium in Europe or US for similar length flts. While food is not much superior than economy, the seat comfort and airport experience (during busy days) is much better. Also, business class guarantees FF miles on 9W as opposed to some of the check fares (you can get the miles in many partner programs - though not status miles outside of their own program).