It seems the F-35 would give them a lot more flexibility for their money.
Not Australia’s decision to make.
No.
Plus, if it was required, they could base F-35B's (the VTOL version) off the two new amphibious assault ships that will be joining the Australian fleet soon.
Having the same aircraft stationed on land as they do at sea would help cut down on the replacement parts and mechanic training that they would be required if they had F-35's at sea and F-22's on land.