from there Sasuke did an Ameratsu chidori and Kuruma had to muster any ounce he had left (that made him go to sleep) for Naruto to do a rasengan
Naruto has multiple variants of rasengan and also odamma rasengan and sage based rasengans but he did a rasengan non the less compared to Sasuke's more fancier chidori
Indra's arrow was an attack that used all of the tailed beasts chakra
I don't think that you think that those small amounts of tailed beast chakra in Naruto plus Kuruma's sage chakra was equivalent to what Sasuke mustered with Indra's arrow, that also had the other half of Kuruma's chakra added to it
Kurama didn't have to muster anything he already had chakra all of which he gave to Naruto trusting him. I didn't see a tired, drained, fatigued Kurama trying to gather/mustet the last of it's chakra.
Naruto didn't have the time to make multiple variants without Kurama helping him so that's fanfic right there. Naruto wasn't holding back either if he was he wouldnt have been out of chakra, immobile and dieing next to Sasuke.
Secondly Sasuke's the stupid one there was never any need for him to clash with the Rasengan, his eye allows him clarity of sight to avoid and take the kill shot. And he would've blow Naruto away instead of blow off his arm and destory the area as he did.
Lastly Naruto has 6psm chakra not just a little bit of tailed beasts chakra. On top of that the entire chakra of the tailed beasts can only only be contained in the Jyubi because they are chakra themselves, not in a PS which is 50% kurama avatar size. And if it was as you say they wouldn't have still been sealed in the chibaku tensei.