So your question seems to be about the fluxbox menu once it's started, correct?
There's lot of things you can do with it--I have a little, albeit dated page on it at
http://home.nyc.rr.com/computertaijutsu/fluxbox.html
It gives possible key shortcuts, etc. For instance, in my fluxbox session, I can open xterms, browsers, move windows around, etc etc all without touching the mouse.