First of all, I don't seem to remember Nocturnal getting all angry about that, and secondly even if Nocturnal wasn't to pleased with what was going down, it wasn't an invasion of her realm, it was just on the way to Mundus.
It wasn't Dagons intention to invade, and she might not have been at first but I'd imagine she was pissed Dagons forced started slaughtering her minions and occupied the realm anyway. On the otherhand, Nocturnal isn't really the type to get angry, I imagine she was just moping somewhere in a dark corner.
First off, I discussed Malcath and Merdia (both of whom cannot be readily classified) but regardless, who says? That whole wheel thing reeks of inconsistency.
If you believe the theory of antithesis, you must reject the wheel theory and the limited classifications of "Aedra" and "Deadra".
That still doesn't explain why you have to drag in the Manga-Ge and every other odd exception. Sometimes generalizations are a bad thing, especially when it's those exceptions that matter, but right now it's not relevant.
For Mankar's idea that Mundus is yet another Daedric realm it doesn't matter that Meridia might have come from Aetherius because right now she has her realm in Oblivion, neither does it matter that supposedly Trinimac became Malacath (or was replaced according to Gortwog) because Malacath has a realm in Oblivion.
If you want to discuss those points specifically, make your own thread and provide a glossary of terms because http://www.gamesas.com/bgsforums/index.php?showtopic=758815&st=40&p=11005458&hl=trinimac%20%20malacath%20%20antithesisentry11005458 you got everybody horribly confused.