Re UAP/UFOs, I think your attitude is sensible. In fact, it tracks with mine as expressed above in the thread. Opinions that track with mine tend to be sensible.
I quoted Shakespeare's famous line from Hamlet to close my post. There's another famous line that goes to your point about the inability to say "I don't know." It's a paraphrase from Socrates, a guy who's on anybody's list as one of the top-5 thinkers in the history of our race:
The wise man knows how little he knows. The older I get, the more true those words ring.
As for "religious nuts and atheists," I'd amend that to read "religious nuts and atheist nuts." Large numbers of believers are not nuts and I've certainly known some atheists who were not. But of course there are also no shortage of people from both categories, religious and atheist, who do fit the "nut" bill.
Nuts are commonly zealous and judgmental...displaying both traits to the point of fanaticism. It's a trademark characteristic of psychologically insecure people, which nuts generally are.
However, the larger point is that there's a critical difference between certain knowledge of the sort one may have with a basic fact of science...and on the other hand a reasonable belief of the kind that is not within the province of science to confirm but can be supported by observable evidence and logical deduction. Religious faith...and the rejection thereof...are both in the latter category.
Going back to the UFO/UAP issue, I think your first three hypotheses collapse pretty quickly on logical inspection, so I lean to #4. But "something else" encompasses a large number of possibilities, some of them, as I said in my earlier post, outside the realm of human comprehension, which is why I also said "I don't know."
I will add, however, that the notion of unimaginably advanced beings defying all known laws of science and physics to travel to this planet just to play peek-a-boo games with assorted mystified humans seems a little off to me. Not ruling it out but I think we need to consider possibilities outside the three-dimensional box for other potential explanations.