Thanks, all, for the perspective and advice. Clearly, I did not grasp the size of Australia !

The idea of one-ways from USA-Cairns and Japan-USA had not occurred to me. in reading postings, it always seems ingenious how people use open jaws and stopovers to make the most of their miles.

It would be nice to burn the Delta miles and keep the US and AA as intact as possible for 2016 ... but not if it costs me 30k extra miles. Thanks for opening my eyes to a different approach.