This is one of the highest-competition routes in Asia, so my thinking is that you should look into buying a ticket outright, instead of using so many miles. I bet if you use cathaypacific.com you could find something, though they may be more expensive. Try BR or CI, and also I bet some cheaper 5th-freedom alternatives, like TG, probably fly the route as well.
I'd be surprised if you don't find something for less than $150 in Y, $300 in J. Good luck!