1. There are so many vairables to speed that it's impossible to give a good number. 10-11 is nothing to be ashamed of, for sure, especially on a mtn bike.

2. If you live in a rainy area, fenders are worthwhile. I'm not a huge fan of bells, but being that half of your commute is on a bike path, I'd install a small one to make life easier. Also, make sure you bring your cell phone (if you have one). Aside from that, you have the essentials covered.

Good luck & keep us posted on how it goes.