Australia uses PAL video standard so it should be fine.
Typically 730 x 576 pixels at 25 FPS
Most recent DVD players in Australia are also capable of playing NTSC and converting the output to PAL standard.
Converting to PAL as you have done is the safest method to ensure correct replay.
If it comes to detail, my understanding is that DVD players output whatever format is on the disk and the TV set (or projector) responds appropriately if it has multi-format capabilities. New TVs are both PAL and NTSC capable. One of our older sets won't show a NTSC DVD even though the player is quite happy about them. Not all DVD players are multi-region code capable.
Quite true but most DVD burners don't add region information unless you specifiy it in the authoring software.
Hence the burnt DVDs are usually multiregion unless designed to be region specific.
If you render for PAL, you should use in the mainconcept mpeg-2 the template "DVD Architect PAL video stream" (or widesceen) to generate the correct settings for the DVDA. If you do so, the DVDA will not render the mepg-2 file again.
Audio should be rendered to AC3-Stereo in a separate render step (or 5.1 off course).
The DVDA must be set then to PAL, too.
Or if you use another authoring too, you should apply the template "DVD PAL".