That nauseating spin sounds like benign paroxysmal positional vertigo (BPPV), caused by displaced inner ear crystals. You might want to research the Epley maneuver and similar and talk to your doctor - it's a trivial procedure that might fix that.
I thought the displaced inner ear crystals would cause chronic vertigo rather than paroxysmal positional vertigo. At least from my experience with my mother. Sudden falling sensation, and her trying to hold onto the arms of her chair as if she is free-falling even though she is sitting down.
What he is describing sounds to me more similar to how I feel when I often feel lying down on my back and under the influence of Cannabis. Turning to my side immediately fixes it without exception. It isn't necessarily a falling sensation but rather just nausea and the world starting to spin and accelerate, until you turn. And I do not have this when I am sober.
