I haven't read this entire thread, so I apologize if someone has already asked this. I'm curious if you can point to any report of an event that is undeniably some god acting in the world--even by the metaphysical and epistemic standards of the day in which the event was supposed to have happened, or alternately, when we think it was written down? Let me explain by way of example:
Take the incident in Exodus with the burning bush. It was probably fictional, but was believed to have been historical fact by a sufficient number of people to qualify here. The question I'm asking is whether people at the time might have, by their own epistemic and metaphysical standards, have thought something else was going on? It seems to me that it is almost surely the case that this was not recognized as a genuine instance of the interference of a god in the world. In fact, Moses himself expressed some very significant skepticism, and he was experiencing it first hand. He asks, first "how do I know it's really the God of Abraham?" Then he asks why in the world God would choose him. Then he asked how the other people he was being sent to would know that it was God, and not something else. Then Moses says "I really don't believe you," so God tells him of a few signs. He saw them as signs that any magician could do, and basically said "look, no one is going to buy that--you're going to have to find a smooth-talker, 'cause I ain't doin' it." And then God got really mad and said "hey, don't you have a brother?" and Moses, apparently not wanting his brother to be threatened, decided to go back to Egypt. But then apparently his wife, Ziporah, was skeptical, and so God had to threaten to kill Moses.
Now obviously some people--namely the Hebrews--did come to believe that it was God. But the Egyptians had their doubts, and many eventually died for those doubts, according to the story.
So now, today, there are obviously plenty of people who believe that God unambiguously acts in the world. But then there are skeptics as well, and I take it you're asking for something that would convince all, or most, skeptics--you know, like how it was in ancient times. But that never happened in ancient times. Not once that I can think of.
Now, if you're asking for something else, please clarify. But the premise of your question is flawed as far as I can tell, as described above.