Not sure where you are tring to fly from....

What you can do is look to travel from other airports...partivularly on the west coast.

I know Delta you can do this but Im not sure if you can on American---look at Alaska Airlines routes to Hawaii...they fly from all makor cities to all 4 islands...you could use your AA awards to book these flights then fly separatly to these airports.

The baseline rate for Hawaii is 40,000 miles for RT. Another option to look at is use your AA miles to fly to Honolulu (HNL) for the back/forth and then book separatly the HNL-KOA portion

As for the island itself...

AS another OP said there are 3 ways....

1. through Waimea to the north

2. Saddle road in the middle

3. Southern route

Many rental car companies proohibit you driving saddle road.

What you can do is just make the trip a loop trip.

The southern drive brings you through Coffee plantations to the south of Kona, then through Lava fields...down to the souther point of Hawayy (most southern city, most southern post office int he US , etc) and off shore at certain times of year you can see whales. Near the southern point is a green sand beach.

Then when you start toward to north to Volcano you have a blank sand beach right off the road....its about 45 min drive from Volcanos NAtional PArk. From the park its about a 30 min drive to Hilo. Its shorter to go from KOA to volcano through Hilo.

Near Hilo you have Akaka water falls (hopefully I didnt butcher the name).

From KOA to Volcano it will take 2.5-4 hrs drive depending on way you drive and traffic. The large island has virtually no expressways...they are local roads. There is a few mile stretch near Hilo and near Kona where the road turns into an expressway because it has interchanges.