It works, at least with one button and corresponding LED, no reason it shouldn't for more.
But it does not work without throttling the loop, here probably more severely than necessary, I would guess:
// delay(100);
The pushButton.h library code has the word bounce in it, so it seems like it might shouldn't care if it was called at a high frequency.
I'll put that library on the list of push button libraries I have not yet torn apart. No time/energy for yet another. One I have seen doesn't like being called too slowly - no good reason for that to need to be, either.
Maybe there is something I am missing.
a7