Well I have followed this thread with interest. The reality is that Qantas process their seat allocation in a different fashion from most American carriers. Australians tend to like the way Qantas do it, and Americans are sometimes surprised that it is not done the "American" way.
Jet Away, let me address your last question.
Two months ago you asked the US agent to request Sydney for certain seats.
You did not receive a response. This is a breakdown in service by Qantas, which is not good enough.
However if I did not receive a response, I would have been following it up with Qantas much sooner, and not waiting some two months. At that time ringing Sydney direct would have been the way to go, as others here have suggested. Or at least ringing the US agent.
You may well find that you get allocated seats that suit you on Qantas, either by calling them, or at check in. Good luck and enjoy your trip.