With regard to decoupling capacitor placement - one lead should be connected to pin 16 and the other lead should go to directly to Ground (the Ground bus itself, as opposed to going to some point that's connected to another point that's jumpered to Ground.)
OK?
The board that I made for this display
uses 9 '595s - none of which gets "decoupled".
(There is one 1uF across +5/supply on the board.)
Rarely will anything on this level flop for lack of adequate decoupling.