If crediting to AA, then you might want to look at booking the AA codeshares to Australia rather than the Qantas flight numbers. If you book on aa.com or over phone with AA, they can book you on AA flight numbers and so will be eligable for 100% mileage accrual

Do compare prices since sometimes there will be a price difference between what AA offers and what QF will offer

As far as award fees goes, nothing to do with Carbon tax but just simply that Qantas charges significant cash surcharges when booking award flights using Qantas points. AA does not do the same ( other than for redemptions on BA and on IB )