No, definitely not, you cannot change the notes of the chord a bit to make it fit in with the rest of the song. That has to be the most extraordinary thing I've ever heard a pianist ask. It may be permissible to add a octave note at the very end of a piece and only if it's the last chord and if one thinks it will fit the moment (better) at the time, but to change the notes of the piece... I am completely dumbfounded.
Unless there is a typo somewhere in the chord (which you could check with other published editions including recordings), Schumann wrote this piece how he wanted the chords to sound. Maybe you don't really know the piece at all. It's one thing to play a piece, quite another to hear it.
Энтони.