I will answer your question.... FWIW...I would cut the salt to 2.5% maximum... seems above 2.5 %, most think it's too salty... Yes, that calculator is correct... Some folks resort to 1 rub instead of 2 or 3... Nothing wrong with multiple rubs... If you have concerns about the 200 Ppm nitrite concentration, 200 Ppm is allowed when a dry rub is used... to be "technically correct", reduce the nitrite by 10% if the skin is on the slab, FDA rules for commercial establishments.. Since you are not commercial, +/- 10% is not significant.... If you do a brine/cure, where you soak the belly in a nitrite/salt/sugar solution, 120 Ppm nitrite is recommended, FDA also... and reduce the nitrite by 10% if the skin is left on.... To be "close enough", shoot for 150 ish Ppm on all your bacon...
I personally use/do the dry rub... I rub and set the belly on a wire rack, in the refer at 38 deg. F for 2 weeks, or longer.... rinse.... dry.... form a pellicle and cold smoke at or below 70 deg. F.... then return to the refer for 1 more week rest, on a wire rack..... that's to let the flavors "soak in" and continue to dry the meat for a more intense bacon flavor... partially freeze and slice... makes some awesome bacon...
Try different recipes and times and temps (smoking temps) until you find a killer recipe... everyone does this stuff different... My recipe calls for 1.75% salt, 0.25% cure #1 and 1% sugar... The 0.25% cure #1 puts the nitrite at ~150 ish Ppm nitrite.... the 200 Ppm and 120 Ppm nitrite, in the FDA recipe, are maximums for the method used.. BUT, being we are "home curing", those are very good guidelines to try and follow....