As to the pilot instructing the people performing CPR to be seated:
I don't know why this is surprising. Landings put passengers at risk-a known fact. A rough landing could throw the rescuer hard against any number of things, other passengers included. Then you've got two or more casualties. Liability would dictate that all FAA mandated instructions be given even in this scenario. The rescuer can make his own decision whether or not to comply, but you can bet that if the pilot didn't command all passengers be seated, and the rescuer is seriously injured, he or his family would probably sue the pilot and airline for not giving that person adequate notice of landing or some other similar claim.