Nice work! Most of your method is like mine. I use the same seasoning, sometimes with a little tweak like a SMALL amount of some aromatic spice like mace or maybe cardamom.
I double-grind, too. It takes much less effort to go through the coarse plate. I sometimes use a really coarse plate and the meat blasts through that. The finer the plate, the more effort to go through, and the more of a nuisance to clean it properly. Using a medium or fine plate is easier if the meat has already been coarse-ground. I begin by cutting into stew-sized chunks and I sprinkle the seasoning over those before any grinding.
I chill the meat but not too much because the fat can stiffen and resist the plate. Weather permitting I like to grind outside on a day that's 40F or so. I don't trim fat nor add fat; it is what it is, which varies from one butt to another, but regardless, when frying I never come close to the amount of leftover grease that store-bought sausage will leave.
I make patties, too. I use a scale and a press to make uniform portions. I'll chill them, wrap them individually in plastic, then freeze. It takes only a short time to thaw them before frying.