I'm confused though, wouldn't a more straightforward simple result be:

Votes for Hayden: Tyson, Gervase(Immunity), Monica,
Votes for Monica: Hayden, Katie and Ciera.
Returnees vs Newbies. We know Tyson doesn't trust Ciera (he said so and played the HII last week). I believe the Next Time On scene of Hayden trying to get Gervase to turn on Tyson is a Red Herring.

Yes, it would appear more straightforward. But, Ciera has sworn alliegence to Tyson, despite Tyson not trusting her. Last week she told him that she will vote as he votes for the rest of the game. Clearly, after last week, we noted that Tyson did choose to vote with Cierra and against Hayden/Caleb. So, that tells us that he trusts her or at least is choosing to use her against Hayden this week.

That's why I believe that Gervase, Hayden, and Katie will all vote for Monica. This was a great move on Hayden's part because he is able to employ Gervase to vote out his rival, Monica, while not directly voting out Tyson, but realizing that the purple rock could indeed get him out. It gives Gervase an excuse...

Regardless, since Gervase has the IN, and Monica is the target, then ONLY Tyson is still there to draw rocks, the odds are 33% : 66% for him to draw the rock.