Use an Aussie card which doesn't have the 3% international transaction fee. That way you get the MasterCard or Visa exchange rate which isn't too bad. Commonwealth Bank has one or two fee-free cards
Good enough. I went via OA and started the 65k transfers immediately. After the second free year of the OA I did an out/in, came back in on exempt and then got the O meeting the 65k transfers, so I never had to stump up the 800k
If you're on an extension it's easy. I was on non-O retirement extension of stay, so I simply left without obtaining a re-entry permit which effectively cancels the extension of stay. I flew to Sydney, applied for the DTV through the Sydney Consulate, approved within a week, flew back to Bangkok, got that beautiful 180-day stamp. Since then I've left and re-entered twice, each time getting a fresh 180 day stamp