Do subjects you like, as you will tend to do better in them.
That said, keep MAths ext 1 if you find it ok, as a good result will boost your atar substantially.
You have heaps of time before you need to decide what want to do. Many people in yr12 at my school had not much of an idea.
Concentrate on getting a good ATAR at the moment, as it will open up more choices.
Well done on going well so far, but remember only yr 12 counts to our atar
1500 words seems a lot.
Anyway, different people memorise differently- whether reading it out aloud many times very quickly, highlighting, writing out quotes, or writing out in full(very time consuming)
Make sure you understand your topics before attempting past papers.
That said, past papers can be a good way to gauge whether you know a particular topic well enough.