To be honest, I think the bottleneck problem wasn't just at the start - we were having problems overtaking all the way through even as later as mile 10 or 11. Given that large parts of the course aren't particularly scenic, it must be possible to create a route which provides more than a single lane next to traffic particularly with this many runners.
That said the support was brilliant and the weather excellent which always helps.
If you're running less than 45 minutes then you're be fine without eating first, particularly if you've had a decent low GI carb meal the night before such as pasta or rice.
*Do* drink before you go though.
Oh, and eat a decent 80/20 carb/protein food within 30 mins or so of getting back. I generally go for a homemade smoothie with oats, milk, banana, protein powder, honey and frozen fruit, but there are plenty of other things that work well. Porridge, flapjack, toast and peanut butter etc.
EDIT: Oh, and rice and pasta should really be wholemeal to be low GI, otherwise it's medium/high GI. You want a slow release meal the night before then there'll be energy to spare in the morning...