You're about right - 10k worldwide. So you've got at least 1000 business class seats full at any given time around the world.
In terms of routes that Boom's proposed plane can serve, you've got at bare minimum New York to London and Seattle to Tokyo, and lots of connections between Asian capitals where there's much less noise regulation and lots of money. I think their point is that if they can keep noise down, they will be successful operating long haul routes within NA, like LA to New York, San Francisco to New York, Seattle to New York, probably New York to Miami, LA to Toronto. My guess is that they end up with maintenance in Seattle, New York, Los Angeles.
In terms of routes that Boom's proposed plane can serve, you've got at bare minimum New York to London and Seattle to Tokyo, and lots of connections between Asian capitals where there's much less noise regulation and lots of money. I think their point is that if they can keep noise down, they will be successful operating long haul routes within NA, like LA to New York, San Francisco to New York, Seattle to New York, probably New York to Miami, LA to Toronto. My guess is that they end up with maintenance in Seattle, New York, Los Angeles.