I think you are on the right track, but I would make one change.
Use Mr Buddy to warm everything up, and then use a good -40 sleeping bag. That way you are guaranteed to be warm, even with a dead battery. And the bag may seem expensive today, but if you amortize the cost (maybe $400-ish) over the 40 years it is going to last you, that works out to $10 per year, which is pretty darned cheap.
And if you can find a good used one on Craigslist, even better.
If you don't plan to winter-camp in extreme cold, you can get a good bag for a lot cheaper.
Our family often sleeps outside in a Springbar tent at 7000 ft in the BC mountains, in the Canadian winter. Trust me, a good sleeping bag is all you need, and it is an awesome investment. The rectangle ones are harder to find these days but they zip together into a double bed which is very nice.
Two tips - 1. put your water bottle and tomorrows clothes into the bag with you before you sleep. Then your water for breakfast isn't frozen when you wake up, and your clothes are nice and warm when you want to get dressed.
2. The cold weather rating on the bag doesn't mean you will be warm when it is that cold outside, it means you wont die when it is that cold outside. So sleeping in a 0 rated bag when is is 0 outside, will be pretty miserable. If you want to be toasty warm when it is 0 outside, you want a -20 or -40 bags
Cheers
