How hot does the water have to be to kill gluten?
Gluten is a protein, not a bacteria. It has to be removed, not killed. Imagine that gluten is like cocoa powder, which coats everything with a fine film when its spilled. You would use soap and water to remove that cocoa film, cleaning and wiping it away so it doesnt get in your food or on plates, bowls or utensils. Thats the level of cleaning thats necessary with gluten. Thorough scrubbing with soap and water should do the trick.