1. I don't know, check the small print/T&C's on voucher or message the customer services.
2. Depends if you want to be up front and close then the front of the lake, or if you want to stand back and watch the whole spectacular like a large stage show (to get in all the lights effects), then standing back is great, to get a good viewing vantage point, I know that some regulars aim for the large raised up green just at the bottom of Tower street, the one where the Scarefest car sits on. Standing on the front edge of the wall gives you an elevated position over people standing in front of you. Don't aim for the wall situated outside the Towers Street restaurant, this has been used in the the past as the disable viewing and last year as the VIP viewing, you will be told not to stand on the wall. Also don't stand underneath a tree as the branches/leaves will block your view. As a general rule, if you can see the Towers and the sky above it, then you will get a good view.
3. If you want to guarantee a place, the earlier the better. I've seen people securing their spot as early as 4 to 5 pm.
Another tip, if parking in the Car park, get there early and park near the exit barriers, other wise getting out could take a very long time. Paying for express parking next to the main entrance might also be worth considering. Also the there will be various ways to exit the Themepark on the night, going by the past events, you can also exit on foot next to the Sealife, Duel and Galatica etc...