This is a fascinating thread, and it's particularly interesting reading the responses of the JW friends. As is expected, they are simply parroting JW literature without a great deal of thought. I've been guilty of doing the same in the past. As a JW you figure there's no one better at explaining JW doctrine than their own publications, and because JWs turn a blind eyed to contradictions and logical fallacies, they repeat those same statements assuming that those hearing them will similarly accept them.
I think I may have mentioned this on another thread once: I had a study with the husband of a female JW; he was prepared to give it a go and see if he could be persuaded. We were going through the Live Forever book about Bible chronology. When I explained that "a time, times and half a time" was three and a half times (because it said so on page 140 of the book), he asked, reasonably, why times meant two times, not three or four or 22. All I could so was shrug and say, "Well, it just is, it fits."
However I agree that the softly, softly approach is best. It may, just may, be possible that a few niggling doubts creep in over time when your friends try to explain why it is that when kooky things are found in other religions it's proof that those religions are false ... but when those same kooky things are found in the history of their religion, it's OK, because it was just the "truth" of the time that was later corrected.
Few Witnesses are aware of the explicit predictions that have been made in the past by their religion. Heavy pressure was placed on members of the church at that time to accept them, because they were proof that it was God's organisation and proof that the end was sooooo near .... yet those predictions were later dismissed as "false alarms" made with good intent. Today's predictions that the end is sooooooo near are no more reliable than the old, discarded predictions, and they give no more basis to believe that the WTS is God's "organisation" .... or that he even has an organisation.
Keep chipping away. Be subtle.
And don't forget, there are many Aussie ex-JWs here. I'm in Melbourne and there'll be others from your area around here as well. All the best!