Annie, I'm happy that the malt powder worked out so well for you and that it's allowing you to go with the organic flour you were hoping to bake with.
As you move forward, here are a few thoughts.
First, as we've discussed in the past, while bromated All Trumps has the NY style market share by a wide margin and I've heard good things about the Sperry organic flour, I get the feeling that General Mills doesn't put a lot of time and energy into the unbromated line. Knowing what we know about Giusto's, I wouldn't be at all surprised if the High Performance was a vastly superior quality flour to the unbromated AT. What I'm trying to get at here, is that, just because you've concocted a lovely malted blend that's, off the bat, outperforming the AT, I wouldn't necessarily, at this point, just accept better-than-AT as a goal. I would try an .8% malt powder and I'd also try a 1.6%. You may very well end up back at 1.2%, but I'd still see if you can get a little more out of the equation.
Secondly, the KA malt powder feels a lot like it's being targeted towards the home baker, the hobbyist. While KA is a respectable miller, I can't help but be the littlest bit concerned that a product marketed towards hobbyists might not have the tightest tolerances. The enzyme activity in the powder is crucial. Even slight variations from batch to batch could mess with the quality of your pies.
I'm not saying you have to lie awake at night over this, but, if you can eventually track down a commercial diastatic malt, I think that would be a wise move. Because diastatic malt, in it's pure form, is so potent, unlike flour that's cost-prohibitive to ship, you should be able to have diastatic malt shipped from remote areas without paying an arm and a leg. You also might save yourself a little money going this route. 1.2% might not seem like a lot of powder, but, over time, with your volume, it could add up. KA is not renowned for being cost effective.
Again, I'm happy that your malt experiment was so successful.