No you didn't. I think the lack of answers is due to this question being asked many many times.

I will try to offer some good advice;
Be flexible about your dates. Christmas is a peak time for air travel and the airlines charge accordingly... LAX-NRT for example is $586 12/14 to 12/26 but leaving one day later bumps the price up to $1035 (using expedia).

Waiting to the last minute is rarely a good idea especially in peak times. I believe that tickets prices have already started to rise for international christmas travel, the dates and route for my christmas flying has increased in price 30% since I bought my tix two weeks ago.

I've never used priceline. There are websites (of varying quality) out there that will help you find the best price for your tickets via priceline.

It depends if price is more important than miles.