Main thing is that they wait for the QF bus at gate 15 to fill up, that's that "problem".
If they (the bus drivers) followed a real schedule, then that 2.45 is ok, as its on the same PNR, and you would have done OLCI, and shown your passport at ADL airport for them to swipe, so you don't have to approach the counter at SYD T1, which is good thing.
Is the lounge at T1 important to you, if so, try to change the flight to the first dep from ADL.
If the lounge is meh, then giving it 1 hour transfer, and then, few mins security screening, it would "most likely" be that you will have half an hour to walk from immi to where your CGK flight will depart from.
Its Nov, so outside of school holidays.
Edit: today, QF41 dep gate 25 at T1, which is quite a bit of a walk from int security and immi.
Good non slip shoes, min HLO, and be prepared to run, if they don't put you onto an earlier dep from ADL.