Maybe this is the wrong place to ask this, I don't know, but how did you manage to play the 64th note tremolo and holding it to only 64th notes without playing too few or too many notes? Is it just something you feel or did you play it extremely slow in the beginning? If it wasn't for that tremolo I would learn the piece as soon as I could. Is there any other piece I could play as a preparation, something a little easier?