It's quite simple. You cannot, as a rule, manufacture ammunition in a calibre you do not have authority to hold. That means, in effect, that you need a RFD, if you wish to provide a product range.
It is illegal ,BY WAY OF TRADE, to sell unproved ammunition., whether or not you are a RFD.
if you're selling it, it is BY WAY OF TRADE.
You can protest your integrity in reloading techniques as much as you like, but that's no substitute for a proper safety test.
As to the powder/bullet makers data, whereabouts in the range of loads presented do you pitch your 'products' ? That data is a guideline for reloading SAFELY, not a fail safe recipe for you to make and sell reloads. In the small print it will say somewhere that the data provider takes no responsibility for safe use of that data.
As a private individual, or RFD, IT IS ILLEGAL TO SELL UNPROVED FIREARMS OR AMMUNITION, what's difficult to grasp with that?