Hardest part about year 12 is just to keep moving, there can be so many setbacks, but if you stop moving forward you'll just get swamped with all the SACs. I was getting so sick of the whole year 12 July thing, starting August gives hope for a foreseeable future 
Even though I am in year 11 doing 2 year 12 subjects, and my workload is not comparable to yours in any shape or form, I can totally relate. Especially doing subjects with 10 SACs, they're major setbacks. Plus, to secure good ranking, you need to do well on the SACs. Therefore, you need to find the time to learn the content, study for SACs and revise the content for how ever many subjects you do!
Its all about pacing yourself + just moving as you said! Otherwise, you'll be left behind!