Upvote:0
Right now, you're still fine. US rules apply in the US only, Canada doesn't care about US visa rules, all good.
Your problem will be going back to the US, even in transit, because you are still in an "adjacent territory" and that does not reset the 90-day clock. I would advise you to either reroute your travel via Canada (there are direct Vancouver-Sydney flights), or go somewhere in Central/South America (Mexico does not count) to reset your clock before returning to the US.
Another option would be to apply for a regular US B1/2 or transit visa: this will almost certainly be granted, and the VWP limits would not apply anymore.
Also, terminology check: the program that lets you visit the US (and nearby countries) for 90 days is the Visa Waiver Program (VWP). ESTA is the pre-approval that lets you travel to the US.