Well the problem with the APP and Jim Shockey powder is that it is sugar based. Have you ever left the lid off the sugar bowl on a humid day only to find the sugar in there hard as a rock later? Sugar absorbs moisture from any where it can. The problem was you opened one of the boxes. You stated it is humid where you live and I am guessing that once opened, you allowed it to do what sugar does, and thats absorb moisture from the air.

I do not know if you can dry that powder out some how. Send APP a email and ask them what to do with their powder that you purchased that is no good. Then describe the problems you encounterd. Maybe they would let you trade it in. I was also told that pellets are more prone to moisture then loose. Is this because there is more bearing surface on a pellet then a single grain of powder? Who knows.

I would hunt with the Pyrodex and play with the APP until I was certain I could control the moisture in a storage area or containerand then keep the powder in one of those areas until use.