An update! All good here - just received a call from a very kind QF employee in Australia. She understood my situation and helped confirm me on my flights the day before in the same class of service as previously ticketed. AA is now processing the ticket re-issue now that everything is in there correctly. Should be all set within 24 hours. Happy Ending! I was advised the confusion was regarding the MCT. Every time AA requested the new legs citing MCT, they were rejected because the belief was that D/I MCT @ MEL was 70 mins when it is in fact 90 minutes.
Thank you all for the advice, input and for hearing me out. It was very much appreciated for someone who does not frequent the QF forums generally. I'm very excited to fly QF!