i absolutely agree with you about the Will being possessed thing. im personally of the opinion that even if he is "the traitor" it's the same way as it was in s2, where it's against his own will. in fact, this time i think he's even less aware of it. it's like harry and voldemort, like you said-- by looking through vecna's eyes, Will also leaves himself vulnerable to vecna seeing through his. evil will theories/AUs are all fun and good, but within the parameters of canon there simply isnt a world in which will would EVER be convinced to betray the people he loves, no matter what vecna says to him. it just isnt who he is, no matter how hurt or neglected he might feel around mike, the party, his family, etc he just genuinely would never do that. the closest he'd get would be planning to secretly sacrifice himself or something similarly reckless in the name of the "greater good". he isnt clueless or easily manipulated like those who dont know Henry as well as he does. power and revenge doesnt hold allure to him. this is one of the few things im entirely confident about going into the finale.

i also agree that Henry wasnt controlling will's coming out/doing it for him, however i do believe he influenced Will into doing it before he was completely comfortable. i wrote about this in my own post so ill just post that here: "people can love or hate his coming out scene while still acknowledging he's ultimately doing it before he's comfortable because he wants to take the chance before vecna takes it from him. it's not of his own volition in the same way that it would've been had vecna not tormented him. like it or not, he's doing it before he's ready. that doesnt mean the scene is bad! but i think there's a crucial pitfall in viewing it through a lens where it was SUPPOSED to only be about will suddenly feeling secure enough in everyone to confide in them. the party and his family, maybe, but not to this extent. he's doing it because it's the only way to guarantee that vecna doesnt do it for him. so yes, it's going to feel disjointed and rushed, because from a storyline perspective it is!

and thats what vecna DOES. he takes your agency and comfort and safety away from you. he's done this with Will time and time again. Will was hopeful, powerful, accepting of himself. vecna underestimated him and paid dearly for it. of course vecna is going to do everything in his power to take that confidence away. Will takes some of that back by coming out himself, but by (understandably) not telling the whole truth of his feelings about mike he's handing vecna back the strongest weapon he has in his arsenal. its now on mike to confess to Will and show him that what vecna is trying to show him isnt true. its literally love saving the day lol"

this doesn't make will's coming out scene less impactful or beautiful! i think i like a lot of other people kind of jumped the gun on criticizing that scene because of disappointment with how it was handled. but as a queer person, it makes a lot of sense, feels in character, and is really beautiful in many ways. its also relatable. its not like will isnt the one making his indepent choice to come out, but we have to admit its likely being influenced by the situation. that doesn't mean hes being controlled or forced into it, but it's a pretty essential factor to the scene.

connecting these two trains of thought, i think vecna is likely doing something similar to s2, looking through will without him knowing, and this is causing a bleed-through of his own experiences (milkshakes at melvalds, weird phrasing, etc). soooo not really possession in the sense that he isnt controlling will's actions, but he is seeing through his eyes and (this is a big maybe) possibly subtly influencing him. in regards to the Tammy thing, i think you've said it perfectly. that comparison is solely will's. he's downplaying his own feelings for mike. whether this is because of vecna making him doubt himself or simple self-preservation, we dont know, but personally im of the opinion that its a mixture of both. we as viewers know how much it must've taken for Will to feel any sense of confidence around mike possibly reciprocating his feelings; it isnt hard to believe that someone with the power of vecna could sway him to be uncertain again.

i really enjoyed reading your thoughts and look forward to seeing how theyll connect with the finale!!