Hi, me again. So your thoughts I'm sure, are not to much different from anybody starting out, and trying to grasp the thought process to curing meat completely and safely. I have been where you are, only a couple short months ago, and I claim no level of expertise. There are however, fellows here, like Dave for example, that have been doing this a while, and are doing it by the book. Don't be afraid to ask questions, any question, is worthy of an answer. Now, that said, when you get your answer, consider it carefully. Nobody here will steer you astray. I too asked, got answers, and then researched, read a ton, purchased books, and confirmed just how serious messing things up can be.
You are not naive. The amounts required, really are not a lot when you look at them in a bowl or bag, and you are correct in that they may only cover a 4x4" patch on one slab. Consider how few grains of salt it takes to season an egg, or a steak. If you took all the salt and coated one area, it may not even cover a square inch, yet the meat or egg has a nice salt balance. The nitrite/cure, salt and sugar will act in a similar fashion. They will all dissolve, and be absorbed as a liquid into the meat, and pull an amount of moisture out of the meat, you will see this in the bag. You didn't add moisture, but there it is. So as with the salt in the food you fry, the nitrate will also dissolve, and be absorbed by the meat evenly, in an amount, IF WEIGHED ACCURATELY, that will be inline with the recommended amounts accepted, and recognized by government regulatory bodies, and food professionals. If it isn't weighed, or at least mathematically measured, it WILL NOT be correct.