Your wrist lies to the left / right of the track pad area. When you wear a watch or a fitness band, you are constantly rubbing those areas as you type.

Your wrists shouldn't be touching your laptop if you care about ergonomics.

You really don't have an option if you're on a macbook - the keyboard rests a good sixish inches behind the front of the machine.

He means that your wrists shouldn't be touching anything. They should be hovering a couple of centimetres above the flat area in front of the keyboard.

Am I supposed to hold my hands in the air for hours straight? Because I can't do that, or at least it's far, far from feeling comfortable.

Yes you are... doing otherwise leads to carpal tunnel syndrome