The Money Bin at the start of the series is definitely full, but it seems far more spacious compared with how full it was in other sources. Now, thanks to the backstory montages, we know why that is: Scrooge was using his personal fortune to find Della. That's why it isn't as full.
Which provides a plausible facade for Scrooge's greed - it isn't just straight up obsession with money, he's trying to save up enough funds to be able to re-launch the space program again.
Scrooge was so upset about failing Della, he tore the picture of The Spear of Selene into pieces. So then why didn't he just recycle or throw those pieces away? Instead giving them to Quackfaster for storage? Because if he did, he'd destroy the last picture he'd ever have of his niece. As angry as he was at her stubbornness or his failures, he couldn't just... destroy the memory of her like that.
If one pays close attention to the episode, the Sunchaser (while stuck on the mountain) seems to become unstable every time the characters argue or fight with each other, and stabilizes when they calm down. It finally falls off the cliff and crashes when the truth about Della is revealed and everyone (minus Launchpad) participates in a huge argument that ultimately tears them apart. In a way, the Sunchaser represented the relationships between the characters!
Donald's reluctance to bring up his sister is actually quite justified when the whole story is revealed. Regardless of Scrooge's role in the incident, Della still went off into space riding a highly dangerous prototype rocket with no thought towards her own children. At best she didn't think things through, and at worst she just didn't care what could happen to her or her eggs. No matter what Della's intentions were, Donald would have essentially been telling his nephews that their mother basically took off with no thought towards them.
Why did Della think that she could pilot the Spear of Selene solo? Well, she designed the darn thing and probably thought she knew it better than anyone. On the other hand, she failed to account for the possibility modifications might've been made to her original designs...
Dewey is just like Della. All three of the boys are, but Dewey in particular. His thirst for adventure, his recklessness, all of which are highlighted in this episode, but in hindsight are also more apparent in Woo-ooh!. When Scrooge and Donald look at Dewey, they're likely seeing a young Della. Which would be both heartbreaking and terrifying.
Which possibly explains the running gag of Scrooge calling Hewey and Louie by name but only referring to Dewey as "the third one" - it's not that he can't remember his name, it's that he's scared of misnaming Dewey as Della.
Scrooge's decision making took a nose dive whenever someone questioned his ability to keep others safe, just like when Huey kept questioning his skills when climbing Mt. Neverest. Both incidents were due to Scrooge failing the first time around, showing he likely has a lot of hangups and confidence issues.
Dewey's accusation that Scrooge only stopped when it put a dent in his Money Bin is technically true, as he was forced to stop by the board of directors after he drove his company deep into the red. The key difference is he didn't want it to stop. This likely contributed to his anger later, as he might have realized this was the public perception of him.
Donald's last conversation with his sister might've been that argument we saw in the flashback. Scrooge probably had to come clean about what happened given that Donald was seen pushing the eggs away from the rescue control center, but that might've only made it worse. In all scenes relating to the two, Della's always gotten the better of Donald. But the one thing he was right about was the thing that probably got her killed. It's horrible.
In "Jaw$", the town was angry at Scrooge for his treasure hunting hijinks ruining the town and it's played for laughs. But this episode implied that dozens, if not hundreds, of pilots were all sent to their doom due to Scrooge trying to save Della. Pilots likely with friends and family left behind, all knowing that Scrooge knew the dangers but sent them there anyways. It wasn't until this massive loss of life that Scrooge finally stopped his adventuring the first time, so the town likely feared that it's not going to be another similar incident before he stops again.
This could be related to the torn newspaper spotted on the floor back in "Woo-Hoo!", which sported the headline "McDuck hangs up his spats following..."
While the Vultures stopping Scrooge from spending more money on finding Della can come off as cruel, it makes sense given the tons of money Scrooge had spent on this futile project. Exactly how many employees were laid off from all this?
Scrooge apparently owns the land that the town is built on, the deed of which he got from The Beagles. Considering the absolutely ludicrous funds he was spending, along with just how much of the town's infrastructure he controls, he was also likely driving the entire town into poverty. The Vultures may have pulled Scrooge away at the behest of the townsfolk, as Scrooge was probably destroying their livelihoods.
Even before Della disappeared, Donald was already clearly filling in for their father, who was nowhere to be seen, and there was obviously no one to object when Donald took the boys' eggs to raise them himself. What happened to the boys' father?
A bit more physical compared to the econimcal and emotional issues listed above, but the Triplet's eggs are about as big as Della's torso. Ouch.
