wasteful/dangerous to count upon a warming fire.

hostile people might mean you dare not have fire, other than maybe a deep Dakota fire pit to heat rocks and put inside of your shelter or sleeping-gear. Chopping wood is noisy and dangerous, especially if ice,snow, rain or wind, exhaustion, starvation or dysentary are issues as they are likely to be in a survival situation. Best to arrange to have a sealed shelter and lots of insulation/clothing, so that you dont need the fire for warmth. Seriously consider using a bicycle to move south out of cold country, 100 miles per night, if shtf. Get where the growing season is year round, where you dont have to fish thru the ice, where the animals are not all hibernating or migrated from, where you dont have to chop thru ice or melt same just to get your drinking water and where your water filter wont freeze up and be ruined.