There have actually been a few cases that have made it through the courts that apply "employee" status based on how the company treats the worker rather than how they're paid.
Especially in cases where the worker is on long-term assignment somewhere like Google.
Fair enough. I don't know what the maximum height of an individual stack would be, but certainly on the order of "feet" rather than miles, which suggests that any pile would cover an extremely large surface area. I suspect, if such a pile were to exist, it would be distinctly mountain-like.
It's not done yet. The ammophiles will certainly appeal it to the SCOTUS, which isn't exactly rational lately. I'm sure Justice Alito will find a relevant quote from a 12th century blacksmith saying that the Duke cannot legally prevent him from forging horse shoes, and because horses are instrumental to war, are considered "weapons" and thus, the government can't place any sort of restriction on guns because horses are people too, he'll say, citing Tina Belcher.
29ish miles.
A single bill of US currency is 0.0043 inches thick.
$44bil in $100 bills is 1,892,000 inches, which comes out to 29.861 miles.
Maybe not "need", but yes, a fully peer reviewed study confirming or rejecting seemingly obvious conclusions is an important part of the scientific method. It's how we gain confidence in what we (think we) know.