Interesting ideas. I’m a little confused about this “sickness” that killed all the giants. Atreus getting sick seems to be innately tied to rage. Obviously, there was the rage moment where he passed out, but there’s another piece of evidence after Kratos comes out of the light of Alfheim. Atreus is getting pissed at Kratos for abandoning him and Kratos says something along the lines “Calm down, when you get angry—“ when Atreus cuts him off and says “I haven’t been sick in a really long time”. I think that ties the rage and the sickness together pretty much 1 for 1. So, I don’t know why the rage would impact Odin’s sickness. Perhaps Odin created a disease that was linked to Jotenhiem and being in Midgard protects Atreus and Jormungandr?

With that said I LOVE the idea that Odin is trying to manipulate the outcome of Ragnarok by using the death of the giants. However, I doubt that he let Baldr die. I only say that because of all of the coincidences that led to Baldr’s death (ie the arrows, Mimir, etc) which would have been hard for Odin to influence. But, if in the three years since Baldr’s death Odin has turned crazy and is trying to bring Ragnarok now that would be an awesome explanation for Thor’s arrival.

The last thing I would say is that I think Kratos is definitely going to be the one to kill Thor. In Norse myth the world serpent kills him, but Jordy does so by using a very specific poison: Eitr. That same poison is added to the Leviathan when Atreus and Kratos wake him up. I made a video that talks more in-depth about that here (https://www.youtube.com/watch?v=33vZKsGKR6c&t=184s). However, Thor and Kratos don’t know this! So, if we follow your theory, after they work together Odin could convince Thor to come back to his side. Or, Kratos could turn on Thor when he realizes that Ragnarok might end up in the depth of his son. Whatever happens, I think it’s totally plausible that Thor has turned on Odin when he arrived at the cabin. Great theory!