If Kishi wants it to happen, it's gonna happen, that's all there is to it. It doesn't matter if he's out of chakra, if Kishi wants it to happen in the final fight then you can bet there will be a series of events allowing it. The fact that Naruto picked up one of the FTG kunai and didn't just put a regular kunai in his mouth is a very possible indication that he's capable of using FTG. So no this isn't a shit thread, it's entirely possible, especially now.
True.Absolutely no reason to pick it up especially since minato wasn't even around to tell him how to use it.
Yeah I think you're right I just can't remember what he did with it or if it just got destroyed or something.
Well Yang Kurama must have known how it works being inside Minato and all, plus there was Kushina's chakra inside Naruto during that time he could by chance have learned it from them off panel perhaps. Though you are most likely correct and he just doesn't know it.
A Shame really. Could you imagine how cool it would have been to see Uzumaki S/T jutsu VS Uchiha S/T jutsu? Epic!