Well not having Napoleon be such an monumental arse, IIRC he wanted to reintroduce slavery to Haiti and Guadeloupe, would be a good start. If you can find some way of making him give up any dreams of an empire in the Americas sooner, dispose of Louisiana and support the Haitian government either in independence or just autonomy so that relations remain good. You can then maintain and expand upon the already existing cultural links.
All of the colonial powers had legal slavery in their colonies in 1802. None wanted anything to do with an independent black republic. Slavery was justified on the notion that black people were inferior, so how could a European country accept an independent Haiti? It wasn't surprising that Napoleon wanted to restore slavery. His peers would have considered him a monumental arse for
not doing so. The notion of France just deciding to accept the independence of by far its most valuable colony is far-fetched.
Back to the language issue, it's complicated. To say that only a small minority can speak French is somewhat misleading, because the vocabulary of Créole itself is about 95% of French origin, so all Haitians know
some French - it's not a completely foreign language. The reason why the majority don't master French is simply because the school system is a disaster - it's so strapped for cash that in most places, students have to pay tuition to attend school, and Haiti is extremely poor.
To make Haiti fully francophone, you have to have a better-funded school system. Classes in school are conducted in French, and those who are able to attend school all the way through high school become bilingual - but most Haitians aren't able to attend school that long.