Also, unless you have a POD three generations before Napoleon or at least one generation before but you know involving something his parents were involved, there is a good chance he'd probably be born anyways.
No. If circumstances change at all even a short time before the conception of any person, the odds are overwhelming that that person will not be conceived or born. Bear in mind that every conception is a one-in-millions outcome. Conception may not happen at the same time. The circumstances of people meeting and marrying (or mating without marriage) is also very sensitive to circumstances. (Though sometimes overdetermined.) Go back a generation, and billions of trivial events will be changed, any of which could affect the life patterns of historically important people.
Broad trends remain, but anything dependent on any individual will change.