"I suggest you rebook LAX-JFK-LAX sectors on QF codeshare flight numbers for full mile earning. "

This cannot be done. You cannot purchase a ticket for a domestic US itinery on a QF flight. If it was all on the one ticket, then it could be. Also, because it is 2 separate bookings, should the AA connecting flight be delayed and the QF flight be missed, QF/AA have no obligations to rearrange the onward flight to Australia They probably will, but they don't have to

The joys and pitfalls of buying separate tickets

Dave