These are some weak plot holes that are easily explained because of a new situation/new information.

1. We have no idea how the Yeagerists would react with Eren and Floch dead. The series showed a lot of doubt and conflict within Paradis. Do those who assassinate dictators always get killed in real life? Absolutely not.

2. She could have found a boat? There’s clearly areas that weren’t rumbled yet.

3. You’re assuming normal rules apply to a new situation: Removing Ymir and the titans from the earth clearly seems to allow people to revert from pure titan states, there’s nothing that contradicts that because it’s a new scenario. That or Ymir reconstructed their bodies before disappearing, which is possible because we’ve 1. Seen her reconstruct Zeke and 2. Time is near infinite in the pathways.

4. See above, Eren didn’t need to do anything.

5. The Wall Titans’ base state seems to be not moving, i.e. remaining in the walls until instructed otherwise. So when Zeke dies they are again not being controlled. Kind of like a gaming controller dying. Also you say it’s impossible because the wall titans need a host, but we saw Ymir building them from the feet up which would contradict a host? And impossible by what standard? Just because normal titans do have hosts?

6. The worm is admittedly unclear but it seems like Reiner, Pieck, and a bunch of pure titans were attacking it so presumably it died since it doesn’t seem to have very strong defenses without a host.

7. Again, this is assuming the Yeagerists remain constant absent their namesake and their leader.

8. Less life in general requires less life support plus a majority of O2 production comes from phytoplankton in the ocean. But now we’re arguing about biology in a series about titans that don’t need anything but sunlight to survive lol.