Gramos

Qi = Senjutsu He explained this at the time he created the principle of cultivation in this world, making use of something that already exists to create a new path.

Indeed but Raiden is pretty ignorant about the universe of Naruto, he was a casual watcher of the anime and watched some videos about, because of that he believes that knows enough about the world but the truth is far from it eventually he realizes that but so far he's too focus on him to realize

Eien = Eternity

There are many translations but I went with [Shizen Ryūkō] because it conveys the divine vibe of cultivation more. Shizen Ryūkō - 自然竜皇（しぜんりゅうこう）

Raiden's essences exist on a level of existence greater than the Shinobi world, and much greater than Raiden himself. Of course, part of this is also Raiden's assumption. Remembering that there are also bizarre techniques that can make things like Power Levels insignificant. Just note that Raiden hasn't watched much of Naruto or Boruto, which makes him an unreliable narrator.

Yes, but he's only been in the world for a short time, if you don't consider his time cultivating and training, that's just him enjoying himself.

It should be [Cloak of Invisibility Technique] but the translator changed the technique for some reason, I'll try to edit that later.

The table posted by Caelus is a good reference, but not a complete truth. Raiden's system indicates his power level on a scale larger than that of the shinobi world. Think about how a shinobi would survive in a world larger and more dangerous than the Naruto Universe.

Exactly but he'll still do hand seals here and there just because he thinks it's cool.

Yes, but not immediately, only those trustworthy and talented people will be allowed to live in his inner world.