I don't think my father receives enough emotional support from his fiancee...?

your dad kinda seems to be a bit of a pushover & is having trouble standing up to her. & she obviously doesn't respect him!!! if he is more stern with her it will probably take her by surprise & most likely help a lot..he doesn't defend himself & she takes advantage of that & doesn't treat him with respect..once people start defending themselves others will begin to respect them