You could duplicate the layer and set conditions for each.
The first being to dim on non-active days.
The second being to dim during night.
The trick would be to change the opacity on the first layer (non-active days) to what you want it to be. So, transparency is set to 80, no formula. Instead, you change the X position field and use the formula there. So, it'd be $#DOWB#=5?160:-160$ Meaning if it's the 5th day of the week, it'll be in the center of the watch and 80% opacity. Otherwise, it goes off the watchface (-160)
With the day eliminated as a problem, you can focus on the Day/Night cycle.
I haven't used WSUNRISE/SUNSET so I can't comment there. Here's the formulas I've used in the past which may be outdated.
Transparent during day
Transparent during night
Either way, combining multiple boolean conditions is tough if not impossible. You can cascade testing for something (IE: If DOWB=1 set to 10% opacity else if DOWB=2 set to 10%.. etc.. If DOWB=7 set to 100% but you can't say If it's Tuesday and greater than 80 degrees do something. A lot of people have used another field as a way to get around the limitations. (IE: Check for daylight hours in transparency and check for day of week in the X position field)
Hopefully this helps and isn't too confusing.