All separate bookings I'm afraid as some booked with Avios others direct with Qantas. Probably better to not exceed the 23kg per case and pay for additional bags, to be honest it's quite a reasonable cost if pre-paid. Didn't think it worth booking such short business flights at the time as just assumed baggage benifits would be reciprocated.
If returning to the point of departure for some of your flights, you could always leave your luggage at the hotel instead of lugging your bags about.
Most Australian airports are a pain because they charge you for baggage trolleys - AUD 4.00 each from memory - at least at domestic airports. I can't remember for sure because I always make sure I don't need one in Australia because I object to the charge-for-trolleys by principle.
Also I recommend not even think about using the baggage storage places at the airport. They will cost you close to or more than the additional bag charge. AUD 15 per piece per day from memory, so it could well be AUD 30 by the time you get back to pick them up.