The resupply issue is a good question. The problem I see is that by the time you have starved out the Indonesians, you will have starved your civilain population 1st. Nothing says that the Indonesians have to react according to Hoyle. Imagine East Timor in Darwin.
I don't know the number of reactors in Australia, however, what would really be needed is a BREEDER reactor, something that's designed to enrich/create weapons grade materials instead of power. You can modify one to become the other, but it isn't a quick process. After you have the material, you now need to separate out the Plutonium & U-238 from the depleted Uranium. After that... Easier things to do. You also need to consider the willingness of any government to use nukes on their own soil. It becomes a game of "We had to burn the villiage to save it" pretty quickly.
I didn't insert anything into the TL about resistance from the Civilian population, although if I was going to make the TL into something more substantial, it would have been there. I would assume, as I mention in one of replies to BlackMage, that there are a number of veteran's in the area, as well as untrained civilians who would have a problem with what had occured. How effective they would be is an excellent question; my thoughts are that they would be an irritant, but not decisive.
As far as post war butterflies? Who knows? Not just in Australia or New Zealand or even in Indonesia, but world-wide. Even if the USSR falls apart on schedule, what then? The "English- speaking" countries or "The West" will have demonstrated a willingness to stand up to agression. Do the Argentines try for the Falklands? Compared to Australia, the Falklands are a short stroll from Norfolk VA, home of the US Atlantic Fleet. Does Sadaam decide that the West will just sit there and frown when he invades Kuwait; or does he remember the fate of Suharto?
Changes in Australia's gun control laws are likely; maybe it turns in Switzerland or Israel, with every house containing full-on military assault weapons, maybe it becomes like much of the American Southwest, where gun ownership is practically a given for much of the population. I would guess that gun law changes will be least of the changes in Oz.
Thanks for the questions & the feedback.