I tend to agree, it is highly likely that Jerome knew perfectly what he was doing here and if I'm right, it is all Greenwoods fault. I believe Greenwoods mistake was pointing the gun at Jerome for as long as he did, before taking his first turn. I'm not really at home with guns so I might be mistaken but I believe that from the front of the cilinder, Jerome could see what chambers were empty, so when Greenwood took his shot, Jerome had already a pretty good idea that the either the bullet would be in the first chamber, which would kill Greenwood or wouldn't be in the immediate next chambers. And when it was his turn, what looked like some showmanship, he was again just checking where bullet was, making sure that he would see it in a blink of an eye, while distracting his opponent, preventing him from doing the same the few times he might have a look himself. With speech and theatrics he managed to play Greenwood as a fiddle and I think this was the third reason why Galavan picked Jerome. The dude was fearless and theatrical, but also highly calculated and cunning. Greenwood probably never caught on how Jerome did it, but Theo likely knew and was just wondering of his pawn was as good as he appeared to be.