Your math looks odd to me. You look at the amount a book earns in a single year and extrapolate that to the author's annual salary, but seem to assume that once the first year is up, the book stops earning. Does books earning passive over multiple years affect the numbers?

For what its worth, my single non-fiction book has generated passive income for about seven years now.

I fully agree with your larger point that earning a living off fiction is exceedingly difficult these days. I hope fiction authors can find new revenue models like you're exploring that are successful. But I fear that fiction will go the way of poetry and theatre where it becomes a niche art beloved by some but rarely lucrative enough to devote yourself full time to it.