1. No need to worry about funding: if you get an APA or an APA/I. If you don't get one of those, you'll be screwed. But they're not impossible to get either, if you're an Australian citizen. It's not $$$ but it's just enough to live on, if you are good at budgeting. If nothing else, at least you won't starve to death.
2. No courses. Just research your thesis topic for 3 years.
3. No teaching necessary. You can do it a bit on the side if you don't have an APA or the APA isn't enough. But you're limited to 8hrs/week of paid outside work if you're getting an APA anyway.
4. No defence. I guess it's too expensive to fly specialists to Australia, and those who set up the system did it in a time when video conferences didn't exist.
5. If you don't pass the first time you submit, you can just keep resubmitting until you pass. Of course, if you submit when your supervisor says it's not a good idea, that's probably going to be an unconditional fail. But you'd not do something silly like that, well, we'd hope not. The only other way to fail is to drop out. And there's a bunch of reasons to do that! The biggest ones are not being able to get a good research topic, or to not get a good supervisor.