There are a few ways to debug this. First, a blank screen is good. That means bspwm is running.
I would confirm that you're xinitrc looks something like
sxhkd &
exec bspwm
The ampersand is important. Next, try spawning a terminal in your xinitrc to see if its getting positioned properly. It should appear somewhat "centered" on the screen. To do this, use this .xinitrc:
sxhkd &
urxvt &
exec bspwm
If nothing shows up, that means you probably forgot to install urxvt. If it shows up but isn't centered, that means BSPWM isn't getting started properly. Make sure that you've chmod +x ~/.config/bspwm/bspwmrc.
Next, type pidof sxhkd in that terminal you spawned. It should return a number. If it doesn't, that means sxhd isn't running. Try to be explicit and run sxhkd -c ~/.config/sxhkd/sxhkdrc. If pidof sxhkd returned a number, I would open a bug or ask in the BSPWM thread on the Arch forums at https://bbs.archlinux.org/viewtopic.php?id=149444. You could also try changing the Super key to something like Alt in your sxhkdrc and see if that helps.
Did you install BSPWM & SXHKD from Github or the AUR?