Omg I finished TJ route and I can't believe what Chase and TJ had done with Sydney, from what I get it there is like two spirits? I liked your theory but it seems like there is two entities, one is supposed to be Samuel and other the curse that there is in Echo, because if you think carefully and see some details in TJ's rote like the format of the words, it seems there is a evil thing "helping" Chase solve his problems telling him to kill Flynn and everything end right and while that happens there is a conversation with other word style saying things like this is a cycle, we're puppets trying to make him notices that he's being manipulated, but at the same time I think Chase is a bad person with this curse messing his mind or not because it never mentioned him regretting what he's done with Sydney he doesn't feel even a bit bad for it and I thought TJ was good at the beginning but he just looked everything happen and pretended again nothing happened. I think the curse of Echo just make their personalities and wishes more intense making they do these things, like Leo's route he clearly was obsessed with Chase and his jealousy just getting worse as time passed, and the bad end of this route just makes everything more clear, in my opinion there isn't happy end but you got it right lol, maybe I change my opinion as I do the other routes but with everything I know until now I have this theory in mind...
Edit: I was remembering what happened and the evil entity could be a twisted version of Sydney as well, they are like a vengeful spirit, his business was with Chase and his friends so he would make them go crazy, and the twisted version of Samuel don't have anything to do with them so he would be more aware of the situation and try to make Chase fix things and break these cicles of tragedy and revenge, there are some points that don't make sense but I guess it's kind of what's happening, and don't worry I want Samuel to have a good ending as much as you do ;)