YPEA cannot be used as a Destination Alternate but YPLM can?
It can't, actually (without specific RAAF HQ approval). Read your NOTAMs.
Why there are no stop bar lights at Runway holding points?
Are they the things designed to supplement those pathetic (probably ICAO) orange flashing lights in the grass beside each holding point, the ones that replaced the very effective HP flashing lights embedded in the taxiway right where you look?