Be aware that the QFF Oneworld award rules are completely different from the Aadvantage Oneworld award rules -- considerably more restrictive as well as more expensive for similar awards. Presumably the OP is redeeming QFF award, so many of the non-QFF Oneworld award routings would be illegal for their award. The primary limitation is max of 5 stopovers, only 2 transits in any city and 35,000 mile max (vs. the 50K mile max on AAdvantage), and surface segments count in the distance. The OP's base trip is syd-lax-sea-jfk-dca-lhr-edi-lhr-ist-dxb-hkg-sin-syd which is 28K miles.
The lhr-edi-lhr portion maxes out lhr, so ist-lhr-dxb or dxb-lhr-hkg is not allowed, for example. One solution would be stopover at lhr (train to edi or separate ticket), and do dxb-lhr-hkg as the 2nd transit of lhr. That would be 34K miles, so allowed distance-wise.