This goes for all swords Wado has same potential for example to rank up and turn into a black balde not just Enma Mihawk said every sword could turn into kokuto
Yes that is just his training paying off not the sword boosting him same way Luffy who was first one shot just few weeks later was putting up much better fight against Kaido. Zoro already showed excellent attacking speed over great distance when he attacked Queen with his weakest blade.
The sword isn't wielding itself Zoro was using his haki and yes none of the 21 excellent grade swords are ordinary
Same thing him sensing Oden's presence withing Enma makes perfect sense Ame no habakiri would also be the same this doesn't mean Oden is boosting it up from the after life