Simple answers to your questions:
What do you do for living? I breathe air and eat food.
What do you do for a living (wage)? I am a teacher at Smith School.
What does he do for living? He breathes air and eats food.
What does he do for a living (wage)? He is a chef at Smith's Restaurant.
A more direct question is, "What is your profession?" Or, "What line of work are you in?"