Typically a bit less than 1 tsp of kalk can be dissolved by 1 gallon of water, you want have as high of losses from precipitation due to atmospheric CO2, I usually go with 2 tbsp for my 7 gallon reservoir.
My reservoi is 5gal. I have my 5074 hooked up to it. I still can’t figure out how much kalk I need to put in the 5074. I know my correct ratio for when I was adding to my 5gal reservoir but the 5074 has me stumped. Too much guess work.
Generally speaking 1 gallon of RO water will dissolve a little less than 1 teaspoon of kalk. When I have used kalk, I add 2 tablespoons for my 7 gallon reservoir and repeat this everytime I refill the reservoir. I would add 4 teaspoons, but only after you are sure the Osmolator is installed properly, the water level is correct and have run everything to be sure there is no risk of a siphon or other causes of overdose. You can of course add less, adding much more will tend to just lead to premature clogging of the lines and check valve. I would not add more than 5 teaspoons.
Nilsen reactors don't work the same way as a still kalkwasser reservoir. In a still reservoir one can adjust the strength of the solution by dissolving the desired amount of calcium hydroxide. Reactors tend to deliver a more full strength solution as every time the Osmolator pump injects water through the angled inlet into the reactor it mixes the powder in the bottom. I have the 5074 and it works well, but I didn't use it until my tank's demand required full strength kalkwasser.
That is true to some extent, mostly in the reactor you don't have the amount losses to precipitation from reaction to atmospheric CO2 in an open container. This is such a simple reactor though, in stronger reactors that have there own mixing pump, you can mix a more concentrated slurry for example, but in this case, too much tends to clog the hoses, nipples, and check valve, so I would not mix it too strong.