I've created an online calculator. It's in debugging stages right now, and is programmed with the following information:
ppm = 120 equilibrium wet cure, 200 dry cure
volume of brine set at 500ml for wet cure
shows sweetness adjustment factor for a variety of sweeteners
the salt content in Insta Cure #1 is part of the salt basis, you add only the additional salt needed "Add kosher salt"
HOT TOPIC: my research indicated that the rind does not absorb a significant amount of nitrite, so the rind is removed from calculations for brine. If there is scientific evidence to the contrary, please point me to it!
For those with their own favorite calculators or spreadsheets or recipes, please take a few moments and run a test case or two. If you find a variation, error, or bug, please let me know.
Thanks in advance!