I live in Southern California so I do not have the 'winter' problems you face, but I believe most of the people here that do go through snowy winters either heat up the garage like you are planning to do or they use a polymer sealant like
Klasse or Zaino which is durable enough to last through an entire winter season. As I understand it, the main problem isn't slapping on a coat of wax during the winter, rather the problem is in washing your car without having the water freeze on your car and your fingers turning into brittle ice-sticks. There are many threads on that topic. I would do a search and see what you can find.
Mother's showtime instant detailer works fine. I wouldn't worry about that. QDing, your car daily is the best way to keep your car looking nice every day of the week.....and as a bonus, you won't have to wash your car as frequently because it will be relatively clean most of the time. QDing with either MF or 100% cotton will work fine.
The best MF's to use on your PAINT are ones with a plush nap that do not scratch or leave any marring. Perhaps you can decide which one of your towels best fit that description. I'd also suggest getting a few from some of the popular vendors here and compare them with what you are using.
HTH