I'll leave the bike tools to the experts, but for general supplies, I recommend...
* Forever Mini Flashlight - Shake it for power. No batteries. Can hold it in your teeth.
* 9mm handgun - If you're likely to be caught in a risky area.
* Chemical hand warmer - It's hard to use tools with frozen fingers.
* Shoes that you can WALK in, should your bike be irreparable for whatever reason. 12 miles really isn't very far, when you consider the alternative of spending the night freezing to death.