I don't know about your other issues but with the brightness it is probably on the Auto setting which switches the sat nav display between day/night depending on whether the lights are on.
I have found this setting totally useless as the brightest night time setting is often too dim even in the dark, I have set mine up to stay on the day setting all the time and adjust the brightness to suit.
I have found this setting totally useless as the brightest night time setting is often too dim even in the dark, I have set mine up to stay on the day setting all the time and adjust the brightness to suit.