Miko defeated the entire OOTS while Nale could no longer even beat just Elan. It is entirely reasonable for one to be more surprised that an explosion killed Miko than that it killed Nale. And further, Haley never stated that she thought Nale was definitively dead, merely that the presence of Thog proved that he was definitively alive. Before that moment, he was Schrodinger's Brother. Elan was the one who assumed he was definitely dead.
Nale being told something is not the same thing as Nale hearing something, much less understanding or internalizing it. Not when it conflicts with his self-image.
The two images of the rift linked are several months apart, and the rift was still growing during that time.
And finally, something is not a "plot hole" if one can reasonably come up with a plausible explanation for it using just the information given in the work itself, even if I don't spell out that explanation in the text. Not every reaction that every character has is going to be explained in explicit detail. It's possible to draw your own conclusions based on what you know about them as people rather than assuming that the author made an error of some kind.
(And yes, I didn't answer the Ivy question intentionally. The story isn't over yet.)