Eden's Promise talk
Ultimecia is all but confirmed at this point as the final boss. As for the wolf, I feel that your theory could be correct, that it's basically how something sees the WoL himself, as a "guard dog" of darkness/shadow. It could be the first phase we're seeing, where the 2nd phase turns into Griever proper. It's possible that said Griever may use various moves that we have mastered over the years from the DRK job, or perhaps also moves from various other jobs over the years.