A couple of different things:
1) If the whole premise of Slayers is that death row inmates are controlled by gamers, why do they get set free? The exposition video before the Closer interviews Dexter says that the gamer has "full control" of a human being (convict). At least that's how it's supposed to work. But if that's the case, the convict is just a passive participant. So why does he get set free? It's not like he actually earned his way out. He's just an avatar for somebody else who did all the work. Best I can tell, it's more a reward for donating his body for 30 sessions. Now, Kable later comments how it's him that pulls the trigger, as if he's able to have some sort of control in the lag between Simon and himself. But that's not the way it's supposed to work. Castle even says that he thinks the lag is what makes Kable vulnerable. So it still makes the question valid. If the game is working as intended, that the player is in complete control of a passive Slayer, why does the Slayer get set free?
2) For those wondering about the timing of the battles, the exposition interview at the top says that Slayers debuted 9 months ago. 27 battles, that's 3 per month. It's also kind of weird that the Closer asks if anyone has survived long enough to be set free. First, if somebody had, it would be big news and everybody would've know about it. Second, they've only had 27 sessions. So no, nobody has survived 30 sessions because they haven't even had that many yet.
3) I also question why Kable needed to get drunk? Was that always his plan? Before his last session starts, he finds the vodka in his tactical vest. This is seen by a security camera which necessitates him to drink it all so he can smuggle the alcohol into the game. But what if the camera hadn't seen it? He could've just brought the bottle with him and poured it into the gas tank without having to drink it at all and barfing/pissing it out later. So shouldn't his initial plan have been to simply ask for alcohol instead of getting drunk? And then getting drunk would've been Plan B.
4) Whenever they flash the "Slayers" logo up on the screen early in the movie, it's obviously Keith David's voice saying "slayers". I felt like I was watching a Ken Burns documentary for a second. I thought, "Holy shit, is Keith David in this movie?" Of course, he shows up an hour later as an FBI agent. But it begs the question, did Castle get some random FBI agent to do voice over work for his TV show?