M2 is the total sum of all liability deposit money in the US banking system, and liability money has dominated in all monetary transactions since at least 1890. (Dunbar.)
Regardless, it's this line: "Approximately 15% of the real money supply, or about $5,000 for every man, woman and child in the USA, had it been handed to them directly" that I was referring to. That calculation does not reflect what the M2 number actually means. You already have a definition of M2, so I'm sure you can figure out where you went wrong yourself if you just stare at that for a little bit longer.