No, I don't think all the ideas in "The Lord of the Rings" were totally original. I have not read it but I have looked at passages and events within the treatise (my niece was into that kind of thing when it first came out and showed it to me). For example, the power in rings. I am of the opinion that the concept arose during the dark ages and was related to the fact that positions of power in the roman empire were often certified by rings. It was easy for an ignorant person to come to the conclusion that the rings possessed some power or another to control things.
"The Lord of the Rings" is clearly based on a version of that belief. What I said is that behind almost every idea there is a truth. Most of the examples you give are no more than extensions and distortions of some real occurrences. In addition, the plots of most stories are seldom really original. If you look around you can usually find an earlier story with a plot very analogous to what is put forth as “original”. That leads me to believe that, if we knew all the facts, we would find some real event at the base of every story.
Now one could say the distortions are original. That I think I would agree with. But even there I think most of the original distortions are accidental and due to ignorance, not intention. When you find intentional distortion (modern myths created by creative people) the distortions they use are again seldom really original: that is, you can usually find another story on another subject with analogous distortions. Plus that, I think intentional distortion for entertainment is a rather modern invention. I think, in ancient times, intentional distortion was use almost exclusively for power.
Please don’t think that I am depreciating the inventiveness of the people who write these things, I am not. All I am saying is that there are most probably facts of some kind behind every story.
By the way, I hold space visitors as very improbable. Seeing how our civilization is somewhat less than 10,000 years old (clearly too short a time to make a decent mark in the geological record) I would suggest it much more probable that any such signs of outside technology might be signs of an earlier unknown civilization. But that would be another story!
All I can give on anything are opinions.
Have fun -- Dick