Question about 3 settings in custom difficulty?

Im starting a new custom game and I'm not sure about a few settings.

"World gets colder over time": does low/medium/high effect how quickly it gets colder, or how much colder it gets? IE if I pick low is there a bottom temperature cap that's warmer than if I pick high? Or am I mistaken about what this does? If I had it on high does the world just infinitely get colder forever?

What's the difference between "fire overcomes ambient air temp" and "fires prevent freezing"? Which one makes it easier?

"Wake up player when freezing near a fire" Does this mean it won't wake me up if the fire goes out?

Thanks! I'm looking for this run to be super cold and low resource but w/ passive wildlife so I'm trying to keep it challenging in other ways.