The cluck was posted by one of the DIKs, IMO. All the DIKs say several times that "only one thing is clear, there is no traitor among the DIKs". I think that is a clue of the writer to tell us that there is a traitor among the DIKs. I think the main suspect is Jamie. He says two times, I think, that he hasn't been sleeping well lately. In creative writing, that's code for "regrets". And the most obvious thing he can regret is to post that cluck and be a traitor for his "brothers".Riona went to the toilet with the laptop, locked the door, posted the cluck. In the meantime someone knocked on the door and Riona can't go out with the laptop through the door so easily. She is small and probably climbed through the window in the toilet. It wouldn't be the first time that someone climbs through a window in BaD. After that, Riona placed the laptop in the library and sat down in front of the toilet.
This theory with Quinn, Tommy, Riona, Cam is already half a year old.
Cam distracts Rusty.
Riona takes the laptop.
Quinn brings Josy to put pressure on Tommy. Tommy goes out, Quinn follows. the picture of the safe is taken down. The plan probably to put the laptop in the safe. However, Riona could not get the laptop to Quinn and Tommy.
From the way Heather questions the MC, she probably knew about the plan. Otherwise, why would Heather be worried about Tommy.
I think that the explanations of the cliffhangers of this game will be simpler than your theories. Most of them are too complicated to put them into the script of a game like this one. This is not a Hitchcock´s movie or Agatha Christie's novel. How do you think the dev could translate into images and dialogues a plot so long and complicated? It would be half of an update just to do that.
The explanation of this subplot will be something like "one of the DIKs is being blackmailed by Professor Burke to post the cluck because he wanted to force Cathy to resign. That way Jade would lose her best friend and ally at work." We know that Burke has access to DIKs' computer. Probably one of the DIKs give him that access (passwords, videos like the one of the MC with Cathy, etc.). It seems to me that Burke will be the main "villain" of the game at the end.