I am here to submit that the word "nothing" is a positive quality in "Heroes." It is a word that connotes asceticism and humility on this album:
"nothing will keep us together"
Here, "nothing" means abstinence from the destructive vices destroying characters like Joe the Lion and the Silent Sons on the album.
"we're nothing and nothing will help us"
It is helpful to realize we are not important.This will help us remain grounded and stable.
"nothing will drive them away"
These qualities of temperance and humility will drive away the demons that destroyed characters like Joe the Lion.
In an album littered with slithering drunks, jet-setting drug addicts, and small-minded egomaniacs, meekness and purity are the saving graces of all those who will survive and become "Heroes" in Bowie's 1977 Germanic landscape.