Just to be sure on one thing, when he says "The light... It binds them", I think he's just reffering to the bond between you and the scions. Notice that he says that right before getting his ass kicked by the collection of you and the scions
"It binds them" there in particular seems to refer to the bonds between you all, specially given he mentions 'they are too many', not so much binds as shackles but as in bonds.

Or could be wrong, but that particular line is the only thing out of your theory i'd have to disagree with.

(I do have my own particular theory that Zodiark and Hydaelyn are both entieties of the same sort, world-entieties, both in a way trying to compete to stay in the same land/body for whatever reason, i'm still convinced that the dark crystal we saw at the end was Zodiark. Your reading of the Answers theme fits into that too, neither is more alien than the other, though perhaps one is 'newer' to the playing field)