Why didn't Magica have Lena simply kill Scrooge with the diamond dagger and take the dime back in The Other Bin of Scrooge McDuck? Magica needed the dime AND Scrooge. First of all, if Scrooge died before Magica could use the dime, his title of richest man in the world would revert to Flintheart Glomgold, rendering the dime useless to Magica. Second, Magica wants the dime specifically because Scrooge's will is infused into it. The best way to maximize the dime's power is to trap Scrooge in it, as she attempted to do on Mt. Vesuvius 15 years ago. She needed Scrooge alive and uninjured, and she also needed his spirits up, which is why she didn't attempt to capture him within the dime until he got his fighting spirit back. A broken spirit was of no use to Magica.
Why does Magica try to poison Scrooge when he's already in a weak and pathetic state, instead of simply taking the dime? Because she believes that Scrooge is pulling a variant of the Wounded Gazelle Gambit by pretending to be weak and depressed, and expects him to lash out at her if she attempts to take the dime.
Beakley's camera cuts in her guilt trip is her trying to address each of the triplet's sensibilities.
She said Scrooge nearly bankrupted himself in the search, which answers Louie's complaint of him not putting in enough effort into finding his mom.
She said that pushing him away "totally is logical", which appeals to Huey's rationality, showing how he's not acting in good faith towards Scrooge.
She pointed out that at its core, it was an accident for all this to happen, and that it hurt Scrooge so much because he loves family so much, which goes after Dewey thinking Scrooge didn't care enough and that it was his fault to begin with.
When Donald says, "Our family has been apart for too long", it can feel like hyperbole similar to what Scrooge was saying about becoming a Mess of Woe after only 3 days. But if you think about it, you realize Donald's not just talking about the boys. He's talking about himself. Even after moving back in, he's been keeping Scrooge at arm's length, only forcing himself to adventure for family or for accidents. And even then, not exactly interacting much with their circumstance. But after having Beakley spell out how much they'd lose, and how much he'd hurt Scrooge to leave, Donald couldn't deny to himself that he can't keep being mad at his uncle for much longer.
Why is Magica's magic at its most powerful during the lunar eclipse? Her favored form of magic seems to be Casting a Shadow, and the lunar eclipse involves the biggest shadow we can observe: Earth's shadow covering the Moon. Although it creates a bit of Fridge Logic, as the lunar eclipse makes the night darker, thus the shadows less visible.
As much as she has every right to be angry at Scrooge for lashing out at Webby, Beakley is less than willing to keep him and his family separated and is rather direct at the nephews for blaming him. It's understandable since as far as we can tell she has already lost three family members of her own (her husband, son/daughter, and relative-in-law) and her granddaughter is apparently an orphan.
While the series finale Josses this, since it turns out Webby isn't actually related to Beakley at all, it still makes sense that Beakley wouldn't be too hard on Scrooge: after all, Scrooge is one of her oldest friends, and she's part of his family too, whether she wants to admit it or not. She's seen firsthand that he's not the heartless monster they make him out to be.
