So I'll share my views on the ending: It appears that the Sacred Light Continent is just Earth at the era of Christian roman emperors. Augustus was one of those emperors, although he's here portrayed as the brother of the Emperor. To further solidify my theory, the high priest in the Continent is called Pontifex Maximus, which is "The Pope" at that era in real life. Of course it's also worth to note that there is fantasy in play here so it isn't actually like real life Roman era.

Yes the cultivation stages (most of them) and the structure of the universe is from that novel.

Wow man. Glad that you like it