Ostensibly by their own reporting the C3 period held yearly viewership records. Whether that seeming difference is due to diffusion of viewership across multiple platforms or based on people recommending starting with C2 more than any other is another thing.
The subreddit that exists because they got a slight amount of pushback on hating Aabria Iyengar in a different subreddit is probably not the best place to find well reasoned criticism, yes.
Possibly just that Ivan was there even initially because he's friends with the CR crew and was doing them a solid helping get Darrington off the ground. Once they have others to take over he felt more interested in going back to focusing fully on Hunter's.
The Australia shows presumably aren't Daggerheart. As far as we know the Indianapolis show, now confirmed as starring the C3 PCs, is still the first official Daggerheart one shot in Exandria.
The campaign frames do have alterations on certain ancestries. Age of Umbra Ribbets (the frog people) are much larger and more bestial looking for example.
I would note they did say they had other announcements in the tank, they just were put on the back burner as a result of the fires in LA affecting crew and production.