Headscratchers / Fevre Dream

• When does Sour Billy sleep? The book seems to imply he spends all day guarding Julian and running his affairs and at least most nights working under Julian too. Especially when he's running the Fevre Dream and they only move at night. Surely he can't be getting his regular eight hours with that sort of schedule.
  • He's not exactly the sanest of people...
• If these vampires are living creatures that can only be born that way rather than "turned", yet their pregnant females invariably die during a grisly childbirth, how can their species not be extinct? Simple math would dictate that every generation has to be (at most) half the size of the previous one, as each generation's females could only be expected to produce half as many daughters for the next.
  • Maybe they're supposed to usually birth multiple children?
    • It seems a Plot Hole with the possible exception it's not 100% guaranteed, just a danger.
    • It's also much, much more of a problem now that the race has been nearly wiped out. Dangerous and rare childbirth isn't so bad when the species can live for thousands of years while being almost impossible for anything else to kill, but then the "day people" popped up.