well i did Health last year, I didn't get 100% for all my Sacs and I got 40+. You definitely have to be up there in the high 90% for your Sacs, and you need a few 100%up your sleeve as well..but yea just ace all your other sacs (which I'm positive you will) and you'll be fine 
I agree with Machi - there's no rule saying you have to get 100% in every sac to get a 40+ or even 45+ score in HHD (or any subject)

Just make sure you have a stable rank (try to be within the top 3 ranks in your HHD cohort)

As for Social Determinants for Australian Women, you could talk about anything in their social environment or social interactions that has an impact on their health. E.g. their socioeconomic status, whether or not they are employed, income, level of education, level of access to healthcare, whether they're socially stable or isolated, etc

Yeah but for a subject like Health, realistically I should be getting 100% if I want to get 40+, considering it's so simple that A+ cutoff is so high. 
The Health cut-off isn't actually that high!

Generally in the past few years, it's been at an average of about 75/100 for the lowest possible A+ - i.e. if you get a B+ on your exam, that'll correspond to an A+ on your Graded Assessment report

So just minimise mistakes and master your answering technique, and trust me, getting a high-A+ in your exam won't be difficult at all!