Short answers, pulled from the story.
The International Standard Atmosphere is a static mathematical model of how pressure, temperature, density, and viscosity change with altitude. The International Organization for Standardization publishes it as ISO 2533:1975.
The International Standard Atmosphere sets sea-level temperature at 15 degrees Celsius, pressure at 101,325 Pascals, and air density at 1.2250 kilograms per cubic meter.
No. The International Standard Atmosphere treats air as dry, clean, and of constant composition at all altitudes. Engineers add water vapor separately in vehicle or engine analysis after obtaining pressure and density from the standard model.
The ICAO Standard Atmosphere was published in 1993 as Doc 7488-CD by the International Civil Aviation Organization. It uses the same underlying model as the ISA but extends altitude coverage to 80 kilometers, or 262,500 feet, and specifies additional physical constants at sea level.
Airspeed indicators are calibrated on the assumption that the aircraft is operating at sea level in the International Standard Atmosphere, where air density is 1.225 kilograms per cubic meter. Aviation standards and flying rules worldwide are based on the ISA.
NRLMSISE-00 and JB2008 are newer atmospheric models that extend far above the altitudes covered by the ISA. NRLMSISE-00 was developed by the US Naval Research Laboratory and runs from ground to space, using actual satellite drag data to aid predictions of orbital decay. JB2008, developed by the US Air Force Space Command and Space Environment Technologies, covers the 120-2,000 km range and accounts for realistic solar irradiances and the time evolution of geomagnetic storms.