It would be unwise to say too much more about the handwriting, due to the probable influence of drugs at the time, and the possibility that it was written on an unstable writing surface on an aeroplane. This may account for some of the shakiness of the pen stroke.
My feelings about the writing are tinged with sadness. Elvis was desperate for official recognition and status, despite his long established worldwide fame and adulation. His own problems with drug addiction did not dampen his ambition to be appointed a Federal Agent. President Nixon duly gave him his wish at the end of the visit.
It must have been quite a clash of personalities: The leader of the world's biggest superpower and one of the most charismatic, flamboyant entertainers of the era. It sounds like an entertaining movie!