Lack of clarity is sometimes related to the lack of horizontal storytelling, as if the intertwined melodies had been replaced by chunks of vertical, chordish blocks everywhere.
Sing it. Not while playing, I mean. Just follow the score, HS, and sing it ("ta ta ta ta ta").
I'm not sure it will work for your particular piece (I don't know the Fantastic Dance), but for the Partita I believe it will. You get used to the horizontal motion to such an extent that you cease to rely on an (unconscious) excess of legatto and vertical glue.