The target for the cure is 156ppm (between 120 - 200 ppm is acceptable per the USDA)
The tender quick suggested amount should get you there, but you added 1/3 the correct amount. So, 156/3 = 52ppm.
That is roughly how much you added....too low to trust. You need to add 2/3 more, so 52 X 2 = 104 ppm.
The amount of cure per pound to get 156 ppm is 1.134grams. Multiply that by 0.6667 and you get 0.756 grams of cure #1 per pound that is missing (you need to add).
for 3 pounds, add 2.27 grams
for 4 pounds add 3.024 grams
2.27 grams is equal to roughly an almost heaping 1/4 tsp.
I weighed it out and measured it for you.
For the 4 pound slabs, I would add 1/4 tsp. + 1/8 tsp....that will get you real close.
For the salt and sugar,you already added 1/3 the amount you need so add:
salt- 1.66% of the weight of the slab in grams
sugar- 1% of the weight of the slab in grams.
That ought to fix your mistake.
Chef jj or Dave can check my math for you, but it should be close...