If twietee is Helo and the Cylons believe it, he might not live for two more deaths.
It's not next to null. Baltar and Six are both seeking each other out. However since they aren't sharing the same checklist, I don't think their odds increase by a huge amount. Saying it's next to null makes it sound like there is no chance. There's a decent chance although there's also a decent chance Baltar has already been killed.
If 12 is lynched, 12 explodes. So 12 hasn't been lynched. 12 may have been found since we had one night without a death but that can also mean that Starbuck protected who the Cylons were going to off. So the odds that 12 has been found by the cylons aren't null either. It's slightly more realistic that the cylons chose a single individual to kill and it was 12 moreso than the cylons and starbuck chose the same individual to kill/protect. Odds are better 12 has been contacted. But there is no proof other than odds.
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I think that's still up in the air. ravenvii clarified the citizen/human naming when asked but not the bit about the word 'traitor'. I fall either way on that. He may not have seen the query. For now I'm working under the assumption that it was flavor text like the human/citizen.
Assuming a max of 2 deaths per day/night cycle, it's possible that they could scan every single person before they die, so their odds are simply the number of nights times 2 over the total number of people. Since they are looking for each other and not a third party to both of them, their situations are similar. However, six knows not to scan Cavil, so his odds increase slightly. Cavil can also tell him if Baltar is dead (scan dead humans) and it's not worth scanning anymore.