Pretty sure, but not certain, that you can't open date xONEx fares. You need to set the itinerary but date and time changes are free and unlimited (to 1 year from first flight). I just plan the flights, put in dates for everything I can book, then group the last flights 48 hours apart at 1 year out from booking date and adjust as needed later.
Also, I'd start outside of AU and book through AA.
Also, I'd start outside of AU and book through AA.