I'm pretty sure the oil pump nut backing off results in 0 oil pressure, ie an all-or-nothing failure.
I also think that if an engine was ran with no pressure, you'd have similar wear on all parts, not just the one cylinder. There's no telling what the bottom end looks like if the cam bearing (and the lobes, by the look of it) looks like that. My gut feeling, however, is that there is more here than meets the eye. If you're unable to dismantle things any further, you should probably take it to a shop. I would say that the oil pan needs to come off to have a look at the bare minimum, and a used head is probably cheaper than repairing that one.