Nice to meet another tall lady (183cm here)

I know exactly what you mean about some of the guideline weights being too thin....apparently my healthy weight is somewhere between about 62kg and 84kg. I'm aiming for 75kg which for me is a small UK size 14 or large size 12 (I think Aus uses the same sizing as the UK?) but once I reach 80kg I'll assess how I feel and whether to stop there or carry on.
This is a really interesting article on the limitations of using BMI to calculate ideal weight:
Piece of string better than BMI for checking body fat I'm not sure if I'd rely on it solely, but its another way of assessing progress.
Good luck with your weight loss journey