Looking at the nvidia-smi output, you have Xservers running on the gpu. You should be able to use nvidia-settings by setting the correct DISPLAY and XAUTHORITY values, like running as root:
DISPLAY=:0 XAUTHORITY=/run/user/111/gdm/Xauthority nvidia-settings
use ps aux |grep X
to get the correct value for XAUTHORITY (what comes after --auth)