thanks very much for all the advice, its cleared the uncertainties up. i made the change to JFK-SYD-PER following Gardyloo's suggestion. Judging from some of the other posts it mightv'e been ok the way I had it, but decided I didn't wanna take the risk of it being invalidated later on. It might take a few more hours flying time but i can live with that.
as for the rest I think i'm all set. I appreciate the tips regarding maximising segments and how to get the most flights possible but we're actually restricted by time more than anything else. a wedding in one place on a certain date, a birthday in another etc. so although more sidetrips would be fantastic its just not possible.
but inevitably the next question is, which frequent flyer program would you recommend? considering it'll be an economy trip class fare and i'll be trying to use points towards reward flights. i'm not currently a member of any program, based in sweden so most of my flying is done throughout europe but i also try to return home to australia once a year. any input would be greatly appreciated.