Welcome to the forums
To answer your first question:
Internal marks are usually much lower than your final marks; that was the case for me (got somewhere around the high 70's internally for Physics and Chemistry, if I recall correctly). My memory is hazy but I was ~30th out of ~120 for both Physics and Chemistry, top 10 for both Maths and I'd rather not speak about English 🙃. I went to a high ranking school which I won't disclose; ATAR and results in my signature.
Regardless of how I ended up going or how many other people share their experiences and marks, it's actually a lot easier to disregard a lot of this and focus on yourself. Most of the time focusing on the semantics of HSC scores doesn't benefit you, and I reiterate this to everyone:
the greatest impact you can have on your results is working hard (within reason obviously). Forget all the outside noise (except for your peers after trials), because at the end of the day marks calculation doesn't change, your performance does.
You still have Trials coming up as well, this will likely have the greatest impact on your final internal ranking. Try to put these worries aside (and yes, I get that that isn't easy, but do your best!). Boost your rank as much as you can, then perform on the final exam. After Trials, make sure you help everyone in your cohort. A stronger distribution of marks in the final exam will boost you and everyone else. A 90+ is definitely possible in the best case scenario (and even well below that), but most importantly you yourself have to perform.
Hope this helps