Nah, that water isn’t that bad. Yes, the calcium is too low to promote the removal of oxalate in the mash and to promote adequate flocculation in the fermenter. But other than those needs, there is no need for calcium in brewing water.
For a kolsch, I do recommend a bit more calcium for the two reasons above. I wouldn’t take it higher than about 50 ppm Ca since this is a fairly delicate style. Personally, I like to boost both Cl and SO4 since the SO4 helps dry the finish. Just 0.15 gram/gal each of gypsum and CaCl will provide the Ca and the Cl and SO4 levels will be in the 20 ppm range…very modest.
The high bicarbonate content does have to be neutralized or the mash pH will be too high. About 1 ml per gallon of 88% lactic acid will take care of the bicarb. In the case of German beers, using lactic acid is a very important factor in promoting that ‘German’ flavor. At this dosing rate, the lactate ion should be below the taste threshold for most people. So don’t worry there.
Good starting point for brewing water. Don’t even think about dilution with distilled or RO.