Disclaimer: this is from my own experiences this year, I ain't no teacher either soooo-
Late response, but:
1) I read somewhere that as a general rule, keep each sentence below 40 words (of course, as with everything, there are exceptions). It's cleaner, and stops people from waffling.
There was a nice section in John Marsden's Everything I Know About Writing book that showed examples of good long sentences vs bad long sentences. It's a safer option to go for shorter sentences, especially for essays at this level.
That being said, I often waffle in my essays and although I've had a mark taken off in modern for making a sentence too long (I nearly screamed; it was a 24/25 essay), it's never happened in English. Sometimes my sentences go on for ~4 lines in English (not that I recommend doing this).
2) Don't worry too much on including words from the syllabus. It's nice and direct to the marker, but using synonyms also works, and adds a more personal tone to the essay. I don't have any proof for my claim besides my own experiences, but yeah, engaging with the essay question is what you need to focus on, not engaging with the syllabus. Honestly, I'd recommend only using the language of the syllabus if you get stuck, but that's just me.
This is a bit extreme, but I know so many people who fell short during trials because they tried to include as much of the syllabus as they could in their essays (BAD IDEA!!! they were trying to prep for any question by covering everything), as if they would get marks for adhering to the syllabus and not the question. Their essays were all over the place; trying to tackle too many things in too few words.
It sounds like you have a good balance.
3) Well-intentioned, but shoddy advice. A high page count means nada. Just write. Who cares about page count if you know your essay is 1000-1200 words. A 1000 word essay in 3 pages is still a 1000 word essay (that would be so painful to read *shudder* teeny tiny handwriting).
Additionally, bigger writing = more paper, which means waiting for teachers to stop gossiping at the front of the hall and actually walk over and give you more paper, which is apparently a lot of effort for them. I'm still holding grudges, weeks later.
On a different note, big handwriting is easier to read. Teachers love that; it makes the marking process easier. If you've ever been given a sample essay with small handwriting to analyse in class, it's hell in a handbasket.
