Maybe I am not looking deeply enough but it always seemed to me that the general meaning of the song was plain. It appears to me to be a song of lost love, longing and lust. There has apparently been a physical relationship "I turn to face an empty space, where you used to lie" but this is over and the emotion is like "a claw against my gut". The image of the lady in question riding off on a high horse works on a few levels (I assume that 16.1 or 2 is high)from the metaphorical (getting on your high horse) to the erotic (Lady Godiva where are you) to the actual (saddling up and galloping off). Her former presence is seen as a "spark that lights the night" i.e. her beauty lit up his lonely existence.