Good article. You are on the right track.
I don’t know a lot about Australian demographics, so this may be a totally useless suggestion. Here in Minnesota, it turned out that what we needed to do to get same sex marriage was to inform the electorate about who those same sex couples really are. Not some alien creatures, but your friends’ and neighbors’ sons and daughters. The other thing we had to get across was what same sex marriage actually means. Most heterosexuals simply didn’t have a place in their worldview for LGBTQA. The best they could come up with was, “what you do in the privacy of your bedroom is your business.” They never translated that beyond the bedroom to the hospital room, the probate court, the adoption agency, the school, and so on and so on. The campaign here was very grass-roots, and consisted of the LGBTQA community getting together with like-minded members of the straight community to create strategies to educate their less like-minded neighbors and friends and colleagues. That and some pretty effective advertising, featuring families who were facing this question with respect to loved ones within their families.
It worked well, mostly, I think, because most people didn’t feel threatened or marginalized by the campaign. In the end, it turned out that the people who were against same sex marriage were not as rabid as the rest of us expected, and human decency won the day.
Here’s hoping it does for Australia as well (and hoping the U.S. can hold it together for a few more years).