How do I adjust pink salt amount in a brine?

[AKokkinos]

Hi once again, after reading almost all posts here I learned many valuable lessons, but this final question still puzzles me greatly, so I do hope one of the resident experts will come to my rescue.
For dry rubs, the amount of pink salt to use is quite easy to figure out: Use 2gr of pink salt per kilo of meat aiming for the 156ppm final ratio and it won't hurt to cure for a few days more than necessary.

Now on to brine solutions: Both the 2:1 method and the Ruhlman recipes give a recipe for a brine solution, and advise you to cover the meat and let it soak for the amount of time specified. In the US, the 10% salt level applies, so it is easy to calculate the salt needed. How about the pink salt? If I cure a 2kg pork loin or a 6 kg ham or a 500 gr turkey breast (no skin), how do I calculate:
a. the amount of pink salt needed for complete curing at 156 ppm (do I consider only the meat, or both the meat and the water as with the salt)?
b. the days required to brine / cure the meat for complete curing and avoiding the grey ring?
I read somewhere that you can adjust the salt level to your liking, however you should not increase the amount of pink salt beyond the level needed. What is this level for brine solutions per kg of meat?
I do hope that my questions make sense.
Andreas