German Brewing

You'll want to keep it as simple as possible.
One mistake I've made in the past is to overdo it, with my additions.
It's not necessary & will sometimes negate your efforts, in other areas.

Honestly...That sodium and sulfate are so high, I would use RO.
You're already at a disadvantage, having a chloride to sulfate ratio that you can't easily overcome.
There's no reason to continue fighting those kinds of issues, if you have other options.

I'm having some trouble understanding your dilution %.
Something with this spreadsheet seems odd.

Is your Dunkel recipe what is shown, in the spreadsheet?
19.50# of Munich I
0.25# of CaraMunich I

I could be wrong about your grains, but the CaraMunich I that I get is much lighter...Only like 34L.
I think you might find that you need some carafa, to add some dark brown to the color.
But, be gentle...You don't want a schwartzbier.

Definitely go with the RO water and teaspoon of calcium chloride for each 5 gallons of water used. You shouldn't need any acid malt for that grist. Or if you want to simplify it further, just use a teaspoon of calcium chloride in each your mash and sparge water.

A Dunkel grist does not typically include much roasted malts and the water would not typically require much, if any bicarbonate. While the decarbonated water in Southern Bavaria would still include around 100 ppm bicarb, the brewers there do add either saurgut or acid malt to neutralize that component in the brewing process. If starting with a water like RO, there is no need to emulate that elevated bicarb content, only to need to neutralize it later in the process.

The decarbonated "boiled" Munich water profile presented in Bru'n Water does work very well for any beer style from Southern Bavaria. As mentioned, do ignore the bicarb content and don't treat it as a target. The water needs whatever bicarb is necessary to produce a room-temp mash pH of 5.4. I would boost the Ca and Cl to the 20 and 30 ppm levels, respectively.

Ca:12
Mg:17
Na: 4
SO4: 18
Cl: 8
HCO3: 100

Hey Martin! awesome!

Narziss has a full section on the maintenance of the RO membrane in a brewery. He calls calls for 2-10 dH water for dunkel and schwarz. I doubt most are using tap water.

Agreed, membrane filtration is the standard in every German brewery with modern equipment according to Narzis and Kunze. They are starting from a blank slate.

Low oxygen brewing changes the character of the beer so much that it's possible our water profiles will need to adapt too. I haven't looked into this enough yet.