You can work out approximate distances using http://gc.kls2.com/

Those domestic fares are good if you want flexbility, since they allow changes with no cost and allow you to get on an earlier flight if you arrive at airport early etc but they are not generally the cheapest fares

For cheapest fares, I would suggest just going and booking the cheapest fares either online or through where purchased the ticket. These may well be cheaper but there are change fees of around $50

For flexibilty get the pass though they are not the cheapest fares as a rule

I have found an old set of rules for the boomerang pass as used to be called and expect that the rules haven't changed dramatically http://www.qantas.com.au/regions/dyn...ermsConditions