Let's begin something constructive:
What make you think it is fanfic?
You seem to have interpreted the word fanfic as an insult or in a negative way at least. I have never meant it in a negative way, I just found it hard to respond to what I think about a theory, when I feel it looks more like a fanfic.
To answer your question once more ill repeat myself and ill elaborate more.
A theory is built around facts, however, assumptions, based on those facts are added to fill up the few unknown parts.
A fanfic is a lot less built around facts and more on the imagination (fantasy) of the writer.
The part for example in your post about the TRIP of the sage, is almost purely fantasy.
Nowhere in the manga is it implied that the sage met other sages, more like the opposit, seeing how you need immense chakra to be a sage and seeing how the sage went through the world to teach people about chakra, instead of other people teaching the sage. This doesnt mean your story about his trip cant be true, but it is unlikely, if you read the info in the manga.
Next to this, the manga kinda implies that the sage his Otsutsuki family and the Uzumaki are one and the same, under two different names. Kushina says that the sage his sealing ability to create a jinchuriki, is from her village.
This means that the Uzumaki are the same as the Otsutsuki and that the Otsutsuki family has gone through a namechange somewhere in time and that name has become Uzumaki.
The sage is from the Otsutsuki family. The sage is the first jinchuriki and the first one to use that seal.
That seal is according to Kushina, from her village, the Uzumaki village, meaning, the Otsutsuki and Uzumaki must be the same.
Ninjutsu and the use of chakra, was unknown to mankind before the sage has gone through the world to teach people about chakra, meaning the sage didnt learn that seal from someone else, but he created it himself.
I find that more likely than an Uzumaki who teaches the sage.
Hopefully you consider this more constructive.
