Personally, I don't like food processors for making pie crust. I know that it's a hassle, but, I prefer the old fashioned pastry cutter. (I like THIS one, it doesn't bend and is easier on my wrists.) It's important, IMO, to have the lumps of fat be about the size of fat peas or a tad larger. I find that the food processor can mix too quickly, and bring the fat/flour mixture to a consistency like sand really fast. If I owned a food processor, I'd freeze my butter and use the processor to grate it for me, then dump into a bowl and do a quick mix with the pastry cutter.
There could be issues with your AP flour. In the Southern US, it's lower protein/gluten -more like cake flour. This isn't good for structure. Northerly/Western AP flour should be fine.
I notice that your formula does not have an egg in it. I've been using an egg in mine for years. I also recall asking around at World Pastry Forum in 2006, and everyone I spoke to uses an egg. Serious Eats agrees, although they don't use weight-based measurements for their recipe. (arrg!) It's not common in home recipes, but very common in professional recipes. Aside from being an emulsifier, and helping with texture, I suspect that the protein in the egg helps prevent spread. You mix the egg with the water, I generally hold back a teaspoon of plain water just in case adjustments need to be made.
Here's my formula, makes 2 9" crusts:
10oz AP or pastry flour
0.7 oz granulated sugar (tablespoon and a half)
0.1 oz salt (half teaspoon)
10 tablespoons cold butter (5 oz)
1 large egg
2 tablespoons water
If the kitchen is hot, I measure out the dry ingredients into the bowl and put them in the freezer for about ten minutes along with the pastry cutter tool.
If you wish to sub in some shortening or lard, remember that it's 100% fat while butter is 80% fat, 16% water, and 4% milk solids.
Hope this helps!
