i would avoid an alcohol stove in a vehicle, hard to control. A candle system is a smart choice. Sleeping bags and blankets are also smart choices. Chemical hand and torso warmer as well.

A car kit for your situation would also include at least 50 pounds of sand, (in my truck bed in Seattle when it snowed I carried 400 pounds to weigh down the back end and use as traction) and extra blankets and wool ski caps.

Heck even when I run in the winter i carry a shower cap in case my head gets to cold. It is a waterproof, vapor barrier that can trap heat in an emergency