Oh, I can totally emphasize with your plight about writing the semi-final book! I have a series I've been working on in my head for years and I have the same problem... but on to questions (order is in order of priority, so if you can't answer them all answer the first ones first. Some of these are book 9 though some of these are mostly about Darkstalker, you can skip those if you'd like). Some are just miscellaneous.
1. Why did the NightWings abandon their mind-reading and future-seeing powers because of their fear of Darkstalker but kept their animus powers, even though Darkstalker was a threat only because he was an animus and Clearsight saved everyone with her powers? Is there more to this story than what has been revealed so far?
2. What happened to the part of the book that was supposed to rip your heart out and stomp on it? Though of course, opinions vary, it didn't seem that much sadder than other books in the series - did you transfer certain parts that were originally going to be in ToP to Darkstalker or Darkness of Dragons? For that matter, I notice that in WoF almost no characters die if they get more than a very small role (Osprey, Vengeance), aren't villains (Scarlet, Blister), aren't "not-exactly villians, but are aggressive and try to kill the main characters) (Kestrel, Viper), and in a group of characters at risk of death the nicest one always lives (Blaze lives while Burn and Blister die, Tamarin lives while Carnelian and Bigtail die, Webs lives while Kestrel and Dune die). Though I overall love your series, I was wondering if there will ever be a character (not necessarily even a major character) who dies and doesn't fit into those categories.
3. This may be answered in book 10, but how does animus magic actually work - why isn't it capable of bringing back the dead, and how is it determined which animus spell wins if two animus dragons go against each other? How was Winter able to detect animus magic when he was around Pyrite in Book & (maybe he really does have a magic animus-detecting sense?) And why does the Obsidian Mirror have an effect of seeming weird and foreboding when no other other animus objects do that? For that matter, who created the Obsidian Mirror (I have a theory that it was Prince Arctic, and he used it to see where Foeslayer was right before Darkstalker killed him, but I have no confirmation of that...) What other limits of animus power might there be that haven't been discovered yet?
4. The dragons 2,000 years ago in Darkstalker seem to be way more technologically advanced than the modern dragons, and that applies for the SeaWings as well rather than only the NightWings.What happened over those years to set the dragons back technologically, and reduce their population (the tribes in Darkstalker had thousands of members, in the main series just hundreds). Was there some kind of near-apocalyptic event, and if there was, does it have anything to do with how the peninsula with the Lost City of Night on it is a lot more smaller/covered by water in modern times than it was in the map in Darkstalker? Was there another skyfire comet that actually fell on Pyrrhia, flooding it, killing many dragons, and making mind-reading powers obsolete? (That's a theory of mine, but it still doesn't explain why the NightWings gave up the future-seeing powers.)
5. Does Qibli ever get worried that, since he wears an earring all the time, he might be an animus mask like Pyrite and Ruby? It seems like the type of thing he'd notice.
6. Foeslayer mentioned in Escaping Peril that she had once seen a firescales dragon (before she saw Peril), but Darkstalker reveals that the SkyWings already had a policy of killing animus dragons and presumably firescales dragons in infancy before then? So how did she see a firescales dragon?
7. Speaking of which, do only twin SkyWings ever have firescales? And if that's the case, can only female SkyWings ever have firescales? (Because if twin dragons are in he same egg, and their gender is determined by genetics, then they are identical and they'll always be both male or both female. Since Peril had an identical twin brother, that probably means SkyWing dragonets are like some real-world reptiles where eggs at warmer temperatures are female and cooler temperatures are male, which is what makes me think only female dragons can have firescales.) For that matter, if all twin SkyWings have firescales, does that mean one of those ancient twin animus IceWings Winter mentioned in WT also had ice scales (if that's really possible)?
8. Was Diamond really the IceWing animus queen who went insane that Qibli mentions, or was that actually someone else?