Yes I see a couple of problems but only have one experience in doing this on my own pond and Rex (Rainman) did most of the work.

First he told me if you mix the ALUM and hydrated lime together you will end up with a thick paste and not the slurry that you need so do not do this.

Second, I dont think you are using enough material to get the results that you want. How much ALUM did you use in the jar test and how big was the jar? If I remember right we used 300 pounds of ALUM per acre foot of water but would wait for Rainman to respond. But 300 pounds of ALUM for 6 acre feet of water is no where near enough.

The spray should be fine just have to be careful to not trap fish in an area with too high or too low of Ph, leave them an area to escape to. You have to alternate as you apply between hydrated lime and ALUM.

You will see results the same day and mostly overnight if enough ALUM is applied. Look at my thread "On Lassig Pond" for how this worked on my pond.