Typically the left lever is the clutch, right lever is the front break, and your right foot has a lever for the rear break. Not sure what the setup was for the record breaking motorcycle though.
Note that the bike pictured does not have a front brake. So I’m guessing he went back to his starting position at some point to hit the brake pedal. He first probably just rolled off the throttle until the bike got to a much slower speed. “Probably” meaning, it’s what I would have done, having already decided that riding a motorcycle at 150mph in my underwear is a good idea.
No. Usually one of the brakes (I forget which) is actuated with a pedal, and one of the handle levers (what would be brakes on a bicycle) controls the clutch.
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.
Just keeping his legs clear of that 150 MPH tire is its own feat.