I could be mistaken, but I thought he was just doing it as a "proof of concept", not as a regular thing.
my impression we are talking about small scale production for own shooting needs, not a backyard experiment to see if powder goes puff in a fire.
as someone else pointed out, making BP is easy, making it consistent is how it becomes expensive. There are many variables like humidity, material purity, mesh size of milled materials. To accomplish consistency, you need to be hyper-anal with records, not cheap out on equipment, know some chemistry and few other things to troubleshoot your production. As OP mentions, he wants control over Fs which may not be easy to achieve on demand and on tight budget. KNO3 will be a big factor on purity, does he have analytical set to determine that or is he placing an order to Aldrich?
One thing about becoming a good chemist and getting experienced is being very anal about keeping track of the process. For OPs start, I predict him making a whole lot of batches and then trying to figure out why the hell they perform so differently. After some time, it's not going to be fun, may be it will be.
BP can be finicky to handle, easy to ignite. You may mix ingredients by hand and the whole batch goes up in flames, after turd exits the body and underwear change, good luck figuring out if it was static or something got pinched. It gets old quick, but it's a free country. Best of luck to OP, but there is no recipe for experience in BP making or handling, you got to earn it and live.
If you make small, "safe" batches, it's usually not efficient. You can test powder out and load a few rounds. If you make batches bigger, the inherent ****ups will become more epic.
Even something stupid like milling, it's not simple. When you mill say charcoal, you produce x amounts of y size particles. The ratio will be different all the time etc etc etc.