Jesus Christ...
1. The whole content you posted is outdated and contradicted later on, because the combination of Chakras by Indra and Ashura is what gives Rikudo's power, not DNA of Uchiha and Senju Clans. Hagoromo and Negroid Zetsu both said this, making everything from chapter 510 literally outdated and invalid. As it happens, Obito whom you love to call Tobi was a tool repeating everything Madara taught him, who happened to also be tool manipulated by Negro Zetsu. So neither Obito nor Itachi have Rikudo powers. They are just descendants of Indra with diluted inherited power that makes no relevance.
What? :| It's like you read what you want to read because the last time I checked Kakashi receiving Six path chakra from Obito had nothing to do with Ashura or Indra so your little headcanon is as invalid as the little notion of your "outdated" theory when it comes to the same source of material that was repeated in the 4th databook after the 700th chapter.
It was already confirmed that the only part Ashura and Indra played is the awakening of the Rinnegan not the obtaining of Six path chakra/powers otherwise we would not have Dms Kakashi by now.
As for the bold part is just another fanfic again. Like the 4th Databook stated, the Uchiha clan inherited the mental energy of the Sage of Six paths.
2. Obito whom you love to call Tobi admitted inferiority to Nagato by calling him the unbeatable, and along with Konan calling him the invincible in Obito's presence before Nagato invaded Konoha. Kishimoto portrayed Nagato as strongest Akatsuki member, and you think you know more about the manga than the writer? It's about time you get your balloon-shaped head out of Obito's (whom you love to call Tobi) ass.
He's Tobi whether you like it or not. Tobi himself never called Nagato "unbeatable." that was konan. But because you have that cripple's dick so far down your throat, you're too illiterate to read that he ask them a question not a statement. He questioned Nagato's claim to being unbeatable. Next time don't exclude the question mark next time, it changes the context of Tobi's statement.
Tobi himself was called an invisible immortal in the manga, but your too much of an idiot to read that part I see.
Tobi is stronger than Nagato, he gives the orders for a reason and he did what Nagato did at the age of 14 years old. So get your head out of your ass for two seconds and give up on that selective reading of yours.
3. This was addressed. Obito only has Six Paths Chakra when he's Jinchuriki or steals it from Madara or when he has Rinnegan (which he can't use other than Outer Path). None of these forms are given to him, and even if they are given to him with exception of Jinchuriki, he's still fodder in front of RSM Naruto and Nagato.
Wrong. The manga said he had six path powers prior to this regardless if you like it or not. The only thing Obito took from Madara is Six path senjutsu which requires Sage mode to use at all, all other speculations is just useless nothings. Madara specifically stated that he only stole Sage power from him NOT Six path chakra.
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And since Kakashi doesn't have any access to Rikudou Sage Mode, that chakra he received from Obito is HIS Six path power. Nagato is nothing but a fodder to Tobi and that's just something that you need to deal with.
RSM Naruto > Nagato > Akatsuki.
RSM Naruto > Tobi >> Akatsuki