Sacrifice quantity for quality.
There's no point rambling on for 2-3 pages, when you can have a more simple, concise argument which is a lot easier to understand, and seems more logical. I wrote one and a half pages for each essay and that was sufficient. With my handwriting, I can probably fit around 300 words a page - so I guess a word length of around 400-600 words is okay.
Your practise grades seem high, but ultimately it all comes down to how you feel on the day. Just don't worry about the numbers game and try do the best you can.
Also, in 2008 I remember that we weren't given scrap paper to use during the exam (had to write in the exam booklet) - but maybe things have changed since I did the test.