Do you understand that it is the KJV that has used the name "Lucifer" where it isn't warranted?
Which version then is authoring confusion? Your reasoning seems to go like this:
- KJV has "Lucifer" falling from Heaven in Isaiah 14:12
- NIV has "Morning Star" falling from Heaven in Isaiah 14:12
- Therefore NIV is saying Morning Star=Lucifer
But the original word in Isaiah 14:12 is not "Lucifer" but "lucifer", which is the Latin for "morning star". It is also a word translated elsewhere by the KJV as 'morning'. Also, please explain where Satan 'laid low the nations' before he was cast down from Heaven, which is what is implied by the KJV.
I'm not sure but it feels like you're very committed to the idea that there is a conspiracy here. I hope you're more committed to the truth than to a particular conspiracy theory. Sometimes it is difficult to back down from a position once we've invested so heavily into it, but it isn't about 'us' or about saving face.
Here is Calvin's commentary on Isaiah 14:12 (emphasis mine):
12.How art thou fallen from heaven! Isaiah proceeds with the discourse which he had formerly begun as personating the dead, and concludes that the tyrant differs in no respect from other men, though his object was to lead men to believe that he was some god. He employs an elegant metaphor, by comparing him to Lucifer, and calls him the Son of the Dawn; (220) and that on account of his splendor and brightness with which he shone above others. The exposition of this passage, which some have given, as if it referred to Satan, has arisen from ignorance; for the context plainly shows that these statements must be understood in reference to the king of the Babylonians. But when passages of Scripture are taken up at random, and no attention is paid to the context, we need not wonder that mistakes of this kind frequently arise. Yet it was an instance of very gross ignorance, to imagine that Lucifer was the king of devils, and that the Prophet gave him this name. But as these inventions have no probability whatever, let us pass by them as useless fables.