My flight to ADL leaves at 11.05 am since the original QF 6 would have gotten into SYD a bit later.
Normally under such circumstances, I would have called QF to see if they would change my ADL to SYD flight to an earlier one since they also changed my SIN to SYD flight, but in this case I thought that I would spend more time in the QF Dom J lounge instead, and enjoy my shower and have breakfast as well as brunch. They are usually quite accomodating in this case. Also I find that as a WP, when I arrive off an international flight and manage to clear customs early, QF at the domestic transfer desk will often move me to an earlier flight when I deposit my baggage for the onward flight.
I can guest you into the QF Dom J Lounge.
I suggest that you do not change your SYD to MEL flight and play it by ear after you emerge from SYD customs.
I boycotted SQ because of service and food.
BTW, QF needs to re-issue you a new e-ticket. If you do not receive one in the next few days, call them up to remind them since both booking class and flight number has changed for one of your flights. Otherwise there might be problems at check-in.