I think the one line I keep coming back to is this one:
My husband’s stance is to address such things when they come up and just ignore the favoritism from my parents (who he doesn’t gel with anyway)

I think her parents don't get along with the husband. And that is sad. But it also sounds like LW has adopted the same values as the husband. And I think that this might be the heart of the issue.

There is nothing wrong with finding a partner and adopting the same values. But it might mean she has a different relationship to her parents than she wants. She needs to work that out.