QF additional baggage allowances are only on Qantas metal&Qantas number flights. So your codeshare on Alaskan will be whatever their allowance is.
They might let you on with more, but that would be a bonus, and not expected.
(Sometimes you can get away with this where your bag goes through transit to another airline and isn't re-weighed by the new airline, but this isn't going to happen on your itinerary. )
Can't comment on excess baggage and AA.