As for Ardyn trying to kill noctis in episode ignis it was obviously a ploy, Ardyn is known to be a scummy troll of man who likes to mess with people, so he only did that to be a dick and make everyone freak out. He wasn't going to actually kill Noctis since he needed him to become the true king. Plus if you look at the mural in near the throne room you see 4 dudes who seem to represent the bros, its obviously supposed to be a prophecy type thing, one of the 4 dudes in the mural is blind, so Ardyn was most likely just trying to force things to be just like the prophecy.