Dear Dean,
thanks for your very kind words! I'm happy you got some enjoyment out of my essay.
As for the epistemic vs. ontic question, I'm kinda torn about that. I'm not sure the issue is best framed in these terms---after all, what we know, and can know, depends always on what there is---items of knowledge are, in whatever oblique a way, elements of reality, and even at least supervenient on physical matters of fact, provided one tends towards a materialist metaphysics. So what we call 'epistemic' in that sense is really just a particular way of looking at what's there.
In the other direction, we have of course no unvarnished access to what's out there in the world---whether it's behind the veils of Maya or lurking in Kantian noumena, we (re-)construct the world by means of the phenomena, which are all we can directly access. So what we can know depends on what there is; and what we consider there to be depends on how it is present to us. I'm not sure, then, there's really a hard-and-fast dividing line to be drawn---it may, perhaps, be rather a matter of method: we study the world in an epistemic or ontological way.
So maybe it should not come as too much of a surprise that nobody has yet managed to unscramble the quantum omelette---and perhaps, it's a mistake to try, because the world itself is a mixture of the objective and the subjective. So quantum theory, in my view, can tell us something about what is---for whatever that is, it's something that admits a quantum description at least in some sense---and about what we can know---what information we can hope to obtain about the world.
Hence, I'm not sure if whether the wave function is out there in the world, or in our heads, ultimately makes much of a difference; what's in our heads is in the world, too, after all.
I appreciate the disambiguation regarding Wheeler's 'quantum principle'---but I'd like a bit of elaboration (or perhaps, a pointer to the relevant literature). I don't really know about the connection Wheeler drew between undecidability and space-time (vaguely, in the back of my head, it seems I remember something about building space-time out of a logical calculus, or something along those lines), so I'd love to understand this better!
Cheers
Jochen