Here is the deal.... fat does not contain myoglobin so it does not cure per se. But, salting fat has a tenderizing/flavorizing effect (of sorts) on fat. So the salt in Cure #1 and the additional salt in your curing mixture will accomplish this to some degree. There is one kicker, which is time. As seen below, to get the full benefit of salting fat can take 20 to 30 days on thicker fat back.... but pork belly fat is not that thick.Is it necessary to put the cure/seasoning mix on both the fat and meat sides or is it ok to put it on the meat side only since fat does not cure?
If you have ever dry cured a slab of bacon for 6 or 7 days, it is fully cured. But compare that to a slab that has been dry cured for 14 or 15 days and you will tell a difference in the overall flavor, and you will notice the texture of the fat is more desirable. This is really obvious on salt pork or streak-o-lean bacon.
Getting back to your question: With skin removed, I take 1/2 of the required amount of cure for a slab of bacon and put it on the fatty face and all 4 sides. The other 1/2 of the cure goes on the meaty face.