I have both played (winter mountaineering in Wyoming) and worked (field geology) in very cold weather. Keeping my fingers warm when I need finger dexterity was a major problem when working (writing field notes and handling soil samples). Actually, keeping my core warm was not as big an issue. Wind is an added problem.

As for water, we used to melt snow and heat it before pouring in the water bottle, then take it inside the sleeping bag, tucked up against our bellies, like a hot water bottle. Worked, but there always was anxiety concerning leakage of the bottle.