An easy way to test if your gear is up to spec is to spend a night i your car in your driveway.
There are several categories of gear to have i a car
Stuff to keep the car running-YES
Stuff to keep you warm-YES
First aid-YES, but needs work
Food and water-YES
Stuff to signal for help-YES
Do you have a spare tire and the gear to change it? (Ever had to change a tire in -30c with no gloves... OUCH)-YES, and metal feels like fire when handled
Booster cables?-YES
Did you make it a routine to always have over a half tank of gas? YES, actually that is a habit of mine.
Did you check you are using winter grade fuel? No, I run regular but put gas line anti-freeze in during severely cold weather, I carry extra in the trunk.
Sleeping bag rated for as cold as it gets where you are + equally beefy sleeping pad-NO, but I have equivalents.
Clothing for as cold as it gets where you are. Parka + balaclava +hat + gloves + wool mittens + overmittens + wool socks +thermal underwear (light + heavy so i can dress for the conditions) + insulated pants + boots. YES, on all of that.
Firstaid kit that suits your skill level-YES, I have one of those basic orange zip bags and recent First Aid\CPR Training.
Water in freeze proof containers and a way to melt it when you need it-No to first, yes to second.
Freeze proof food-YES, dried fruit, dried soup noodles, sardines.
High visibility vests-YES, one, may also be pinned to outside of car in a whiteout condition at side of road.
Warning triangles -NO, see above.
Signal flares-NO, just a few packs of snap glow sticks.
Chap stick-NO
Toilet paper-YES
Fully charged cell phone-YES
Cell phone charger-YES, plugged into lighter receptacle
Membership in an automobile association that gives roadside assistance-NO, I have always performed my own vehicle maintenance etc.
Somebody who knows which route you will be taking and knows to send help if needed.-YES, if going for a long trip visit, otherwise no.