The scammer signed up for PayPal business account probably using fraudulent credentials. The person whose credentials they stole will probably never know, they aren’t using the bank account or credit cards to steal money, just to secure the account which gives them access to the invoicing feature of the software. The actual scam happens off-platform. A PayPal business account allows you to send invoices to anyone with an email address through the PayPal server.
If you had called the number, the scammer would not be requesting payment through PayPal, they would have you buy gift cards and give them the numbers, or something equally shady. They are abusing the PayPal software in order to get people to call the fake phone number.
I’m tempted to call the number just to see what the scam is, but I probably won’t. That kind of scam baiting is risky if you don’t know what you’re doing and best left to the pros. I may post the number in the scambaiting Reddit sub, though.
They could’ve gotten your email address from pretty much anywhere, an easy hack of a poorly secured e-mail address owned by someone that has your in their contacts is my best guess.