In the parameter where a factor of 0.05 is mentioned , you can set to whatever intensity you like , however that will only take effect if moon elevation is greater than 0. To further enhance the brightness of night , you can increase cubemap intensity in the construction script as shown below :
I am not experiencing any graphics glitches at any point of time in the entire 24 hour cycle. Maybe it has to do with your GPU ? Is it possible for you to try it out with a better GPU? Do you experience this glitch usually , I mean without using my pack ? You can test this by using the default skysphere and varying the sun height.