Regarding Jester, I also think he's a shape-shifter but to me the original Jester is, the Jester we got, like he's some kind of hybrid and the secret organisation on Northcrest wants him back for research purposes or just so they can integrate him in their society, for me the most likely person to not be the original would be Ruben with what evidence do I think that, you ask? Well feelings... So none at all. The demon rabbit to me seems like a off-shoot from the nameless like a little branch from him since I think what gift you choose from the nameless changes the rabbit dialogue, not sure, I'm one of those people who chooses a path and sticks with it all subsequent play throughs, so like the rabbit is not the nameless but it's somehow connected to him, like with the witches being opposite reflections of each other, they're the same being in essence but also different facets of one another, I think the rabbit is something like that but with less interrelation with the nameless.
Also the list of suspects is a lot smaller than I thought it would be, also I totally agree with it.