I wouldn't describe it like that, or say it wrecks his character. He's confused in his allegiances since he still is thinks Inaho is trying to manipulate the princess and apparently was moved by some of the things Saazbaum said. It's stupid for him to be, sure, since Saazbaum unrepentantly spoke of his desire to kill the princess, but Saazbaum was aware of that stupidity when he set Slaine free with the overly dramatic handcuff removal. He had a feeling Slaine might still be an asset to him and damn was he right. S'yeah, it was expected that he might do something dumb like this if you ask me.
I loved how Saazbaum threw in that "well done" at the end though. Even if he's the one who shot the princess, someone needed to twist that knife in Slaine's gut for being so stupid. Went out like a true troll.
As far as the deaths go, I suppose it remains to be seen, but they were both leaking blood pretty badly. I'm also still awfully curious about Cruhteo's death since his kataphrakt powered up after all. You all seem to be taking it as a given that he's dead.