But they're not.....or they would be stormcloak soldiers, not just talos worshipers. As you even mentioned earlier, they do try and arrest and imprison people for talos worship like Igmund the Slakd, and he's certainly not an active stormcloak soldier. So I don't see why it's hard to believe
They're mechanically part of the Stormcloak faction. And Igmund did not try to arrest anyone, he was what was preventing the Thalmor from arresting somebody in the first place.
Contents of the Imperial missive:
Nowhere does it say he's a stormcloak.
It does say he was a prisoner, and the wording implies he was a prisoner
before being taken by the Thalmor. Which actually concurs with what Avulstein's suspicions that the Imperials captured him. Not to mention that the leader of the Legion somehow was in a position to be made aware of it. General Tullius wouldn't have known if they had just abducted some random Nord minding his own business somewhere. And here's some of Avulstein's dialogue, on the topic of Thorald.
He was fighting for the Stormcloaks, and went missing. Everyone assumes he's dead.
If the Empire could "slap down the Thalmor", they wouldn't have surrendered in the first place. There wouldn't be a Thalmor embassy, a private thalmor prison, and thalmor patrols along the roads with Thalmor interrogators and Liaisons in Imperial cities. Even talk to the Thalmor in Markarth, or Elenwyn. They are there purely to keep an eye on the Imperials and make sure they stay in line. That doesn't sound like the Imperials have much "say" at all.
Yet with all of this it isn't enough for the Thalmor, not by a long shot. They want more, yet if they could just smash their way to Skyrim and take it by force, they would have done it by now.
What you call subtlety playing along I call subservience, and that's exactly what they're doing. The Imperials aren't cleverly devising any strategy that I can see. They're not actively pursuing any real plan against the Thalmor that's mentioned. All they talk about is "we don't agree with the Aldmeri" or "we had to surrender". I don't care that they're not happy about it, I care what they're going to do about it. And since they're content to let their own "citizens" get slaughtered for worshiping a God a lot of them worship as well, I don't consider them protectors either.
That's because they're busy with a more immediate problem: the Stormcloak rebellion. After an Imperial victory, General Tullius mentions that he isn't so sure about the peace they've made with the Thalmor. Legate Rikke is even convinced that all of Tamriel will be at war in a few years. Legate Justianus Quintius, writer of The Great War, also seems convinced that the peace won't last forever, and that something will need to be done regarding the Thalmor.
As for Cyrodill suffering more than Skyrim, a ton of Nords from Skyrim fought in the great war. As repeated throughout the game, the Imperials sent the Nords abroad to fight and die, and then the Imperials came back and told them "You know that Ysgramor/tiber septim guy? Yeah, he didn't become a God, shut up about him or you're dead".
Then they become shocked that the Nords revolted....
Yes they fought in the Great War but no part of Skyrim was occupied by the Thalmor, they never had to worry about it, simply because they won the geographical lottery of being the furthest province from the Dominion's reach at the time. On the other hand, I can understand they wouldn't understand because it wasn't their province on the line. Was there some expectations by the Nords that the Imperials only exist to die so Skyrim doesn't have to put up with the Thalmor? The Stormcloaks are no better than those Imperials that place the welfare of Cyrodiil above that of Skyrim. Hence one of the reasons I choose the Legion: the Imperial soldiers and their Nordic allies care about something greater than just a single province.
If they broke imperial law, then so did Torygg by accepting the duel.
It wasn't accepting the duel that was breaking the law. Ufric committed regicide and treason against the Empire. If Torygg somehow won, he'd be let off because he wasn't the one who issued the challenge, he was merely defending himself.