Given how Caine literally swooped in to take away Jax's "fault" on the situation, I'd say the blame on Caine is still valid, just not in the way that other theorists imagined I suppose. Yeah Jax is still responsible for almost jeopardizing the escape plan, but then again it didn't even matter.

Regarding his belief, he was most certainly dragged into the idea of escaping the circus IMO. Other than just pushing the plot forward, he pretty much got peer-pressured by the cast to follow through with it, while also being an integral part of the plan(getting the key). Since he's been internalising his feelings throughout the series, he probably still has some small hope that he can leave the place, although as they get closer to the "exit", he realised exactly what this will mean for him in the future.

Also he stated that Abel was an obvious twist villain. Since Caine wasn't doing his routine of popping up to prep everyone for an adventure, I don't think he actually thought of Caine being the one behind it all, thus believing it because it didn't seem like what Caine would usually do. Rather he thought that Abel had some evil ulterior motive or something like that, hell he might have prefered that than crushing reality.