Use the opposite pins of the buttons:
Make the layout look better. Make better use of the colors of the wires. Fix the buttons, use the opposite pins. Check how the backlight is connected and check what a 'cathode' and what a 'anode' is and fix the backlight.
Then the display is bright. I have not checked the sketch yet.
[EDIT] After @330R wrote about the wiper of 10k for V0, I noticed that I forgot that, so I updated the picture to include the wiper.