Did it take 50-60 hours in ancient times to gather enough firewood to burn a fire for an hour, or does this limit the definition of artificial light to some kind of higher quality oil lamp?
It takes a lot of firewood to produce the same amount of light as a regular lightbulb. Heck, it takes a lot even compared to an oil lamp.
I read "The Prize: The Epic Quest for Oil, Money, and Power" by Daniel Yergin some time ago. One of the things that struck me was just how much of an effect kerosene lamps had on society. It was the main use for oil in the early days, and indoor lighting went from expensive whale oil (or dirty, still-costly tallow) to cheap, abundant kerosene. It provided hours more leisure time every night in the winter.
No
Among the arguments is that wood was far more important to humanity until about the 19th century than any other resource that gets its own age (i.e. stone, bronze, iron). There's some evolutionary biology stuff in it that I find a bit far-fetched, but at least is an original take on things.
If you'd rather just read a review, this one is pretty good: https://newrepublic.com/article/160298/age-wood-roland-ennos...