Aha! Mansfield Park has been my favourite, since the 1980s. Most Austen fans seem to dislike it, and see the central character as weak and insipid. But, I see it as about code switching and timidity, she's clearly an introvert being bullied by the family.

The intrusion of Caribbean wealth is slavery. Edmond should be more overtly concerned about his families wealth, although to be fair it was mainly dissenters who did this, not the recipients of a family living.

She's on the money for naval preferment. Without help, commoner middies didn't make the crucial step up towards post captain. And for preferment, sexual favours by a sister would be common.