Unfortunately, it is very difficult to get to Tahiti on miles, particularly one way. Even harder from Hawaii.
HNL-PPT is only once a week on Hawaiian.

I would call Korean Air back, as the website plainly shows 30/45 for HNL-PPT http://www.koreanair.com/local/na/gd...sp_rm_pa03.jsp
It could be that no flights are available on Hawaiian and they are routing you through Seoul.

You can check on AA.com to see if the flights are available (and/or book with AA miles)

The only other routings will be far out of the way -- via LAX, NRT, or Auckland. (and Air New Zealand is a tough award booking) Even if you could get mileage awards on those options, it is unlikely it would be worth it.

Do you have to go to both Hawaii and Tahiti? If so, can you spend a few days elsewhere on the way (Fiji, Auckland)? If not, and there's no Hawaiian availability when you want to go, cash may really be the only option here.