I fully believe that he's in the service of what I'm increasingly thinking is a sentient force controlling the island

Oh, absolutely. And I wonder if the island itself is the sentient force.

Flailing off into the wild morally as well as physically?

That's the best description I've ever heard of Jack's behavior. He's just reacting, not acting "with aforethought," as they say. That way lies madness, as I suppose we've already seen.