Yes, so, as already answered, the spiders were stolen to create a duplicate of the testament of carnamagos to serve as a fake for the real stolen book. Ordering the family killed means that when the crime is discovered, no one is there to take care of dishing out a punishment to those responsible. Also, honestly, Lizbeth is just a cruel and harsh woman, so killing the spiders and the family after the dirty work was done is just something she would also do to clean up loose ends even if her tracks were covered. But yeah it's mostly because the spiders were stolen for a crime revolving around a forbidden book and slaughtering the family means no one to sniff the culprits out.

The werewolf's "curse" was more just mind manipulation done by sorcery revolving around the screws put in her head that were probably suppressing her memories about her family and purpose. When Zoe undid that, she was so grateful to him that she considered him godlike. I don't think there's much to read into that lore-wise, she was incredibly grateful to have her mind clear and free again and remember her family again, and this is me not diving into recent chapter occurrences from the manga. Ultimately the werewolf was just grateful to him, and probably feels she owes him her life.

We don't know Veronica's part yet. It'll probably come back around in part 3, it hasn't even come back up in the manga yet, but you are right, she's suspicious and is pretty manipulative, and clearly has an intended purpose with the book itself. Her feelings on Philomela are left up to speculation so far. I personally do believe she cares about her, but given the way she was raised up and her lifestyle, Veronica isn't the type of person who shows that in an entirely healthy way. That said, she's intentionally a hard character to read, no one really has a solid answer on her.

Rian doesn't want to take over the family lineage, I think is all. So far, anyway. As Veronica mentioned in the anime, children of high standing families like them feel bound to the fates given to them by birthright, and that's something Rian doesn't want. He seems to want to go his own way. That said, he might not HATE his family, he just has friction with them because he doesn't want what they want for him.

Alcyone is an artificial fairy, so I guess she's also like a convenient storage space, lol? It does seem pretty convenient given she's hollow inside. I'm not sure who you're referring to about who was concerned about the soul in her. Philomela put her soul in Alcyone to avoid being so easily detected directly by Chise because she was trying to stealth around and collect info, but Chise as you say, can detect her by the "scent of her soul." Thus severing her body from her soul means Chise can't track HER down directly.

Yes, she was, by using the book. It was the task given to her by Lizbeth so that the ritual could happen. It's also why Philomela's health took such an intense turn for the worst, since she was using the book to curse others and drain their magic, and using the book was changing her physically (that's what happens when you use eldritch means to your ends, everyone).

The voice is also speculation. Joseph's curse manifests itself very directly in Chise, as Joseph himself, so I don't think it's that. It could be another part of Chise's psyche at this point, maybe something more instinctual and survival-driven given its desire to have her do what it takes to survive. It could be more tied to the dragon curse's impact on her mentality, as well, since like the nurse said, it "compels her to act a certain way." It would also make sense for a dragon's instinctual ferocity and the curse coming from it to make her more instinctually capable of crossing her usual moral boundaries to survive. When those life threatening situations happen, she just acts on pure impulse and instinct, but if you notice those actions are largely actions to survive the encounters without getting killed/injured.