Not in relation to his body which is the concerning interaction. Though contact with a 150mph tire would have had similar if not the exact same consequences as a 300 mph tire.
Yes, you're correct. The man is travelling 150 mph and the top of the tire 300 mph, so the delta is only 150 mph.
I love that a throwaway comment about a man in his underwear got as nerdy as this.
Relative to the (local) surface of the Earth, at least.