The SYD-PPT flight is the same aircraft there and back so you cannot miss the connection.

When arriving at the International Terminal at Perth I usually try and clear Customs in Sydney and then get them to show me as domestic for the SYD-PER leg.

PER seems not to have too many International flights and their staff can be really horrid in Custom/Immigration.

There are now some 3 class services from AKL-SYD which helps out for points.

My other tip is that AA won't let you go AFRICA-EUROPE-ASIA if you came via EUROPE - you have to use the CX flight JNB-HKG which is on a horrid A340. As you're handled by LH in JNB they never know how to post the points properly.