The cyanide pill is Doug.
Look, "Nice Guy Doug" is a very thin facade. You need to read between his indignant denials and threats to find out what really happened back then.
I'm surprised by Betty's sock puppet account, but that seems defensive and further evidence that Doug was off the reservation, and the Breitweisers wanted help. Why would the Breitweisers of all people pull something so desperate for no reason, if not because they'd be threatened by Ernst?
As for booting him from the chat, I guess that was Cecil who blocked Doug. Cecil is Kelsey's friend, and was probably following all of this straight from Kelsey before I even heard about it. But I'll definitely believe Kelsey before any of these other characters.