2. How to set the brightness level and display mode of the pulsing light?

You can set them in  Settings -> Display -> Indicator light control.

And there're 3 control options:

Brightness: set the brightness to a fixed level or make it change according to the current volume level (check the option 'Follow the volume' );

Charging: set the light to be constantly on, pulsing or OFF during charging;

Working:  set the light to be constantly on, pulsing or OFF when the player is in normal working status