Regarding point 4, it has nothing to do with unbanked people. The demand for stable coins comes from exchanges that don't want to deal wih US financial regulations.
Exactly. If I want to borrow your comic books and lend them out to my friends for a fee, I can pay you a cut on the money I make lending them to my friends. I can't do the same thing with money because then I am a financial institution. So instead I use stable coin crypto because that isn't money.