Standard pressure is 1013, not 1015 hPa.
Nautical Miles are used to express distance both below and above the transition layer.
You're right on 1013. He was taking speed in the second part. Mach is relative to speed of sound, knots is relative to a nautical mile, thus the differentiation regarding speed based on altitude.
How does cruising at Mach .85 make him arrive a few hours earlier than an A380 cruising at .85 or a 777 cruising at .84?
He said commercial, not newest commercial.
Average cruise for long range commercial aircraft is 500 kts or Mach 0.75 .
Cruise (aeronautics) - Wikipedia
I'm also sorry for being off-topic, but someone was WRONG on the Internet
Indeed.