A54
I answered my own question; a typical psicrystal can't use Hidden Talent + Practiced Manifester. Without manifester levels, Hidden Talent doesn't stack with Practiced Manifester. With psionic class levels, they stack.
A56
By the RAW, Metamagic School Focus can apply to "a metamagic feat." It's a reasonable stretch to allow its application for up to 3 feats so long as the spell slot level never goes below its original level.