"PNG" is an abbreviation for the Latin phrase "persona non grata" that is used when diplomats and other government workers are expelled from another country. If Greer was "PNG'd back" to the United States, it means he was suddenly deemed unwelcome in Karachi by the Pakistani government.
The famed "seventh floor" at the Central Intelligence Agency is home to the office of the agency's Director, one of the most influential individuals in the global intelligence community.
In the pilot episode of the Jack Ryan TV series, it's clear that Jack is grappling with intrusive memories and traumatic flashbacks, both key symptoms of Post-Traumatic Stress Disorder (PTSD). The metronome next to Jack's bed may be part of an Eye Movement Desensitization and Reprocessing (EMDR) therapy regimen Jack is trying in order to combat his PTSD.
Washington Memorial Hospital is a fictional hospital in the D.C. area, however the Johns Hopkins Medicine complex in Baltimore, Maryland, does have a cutting-edge Bio-containment Unit with facilities for treating patients suffering from highly infectious diseases or "high consequence pathogens."
Joe Mueller's request for a tip about North Korea is a thinly veiled invitation for Jack to participate in illegal insider trading. In the Jack Ryan novel 'The Cardinal of the Kremlin' Jack mentions to Greer that the Securities and Exchange Commission has contacted him to discuss suspected insider trading and insists he has enough evidence to prove his innocence.