re: Katte's protestations of Protestant faith in his last weeks, I would argue that while hoping for clemency from Friedrich Wilhelm might have been one big reason, another was his own family, specifically his own father, to whom hearing Katte died a good Protestant would be a comfort.

That reminds me, I'm sure you're familiar with the passage where one of his instructors when he was younger wrote that Katte was not too interested in religion, just in pleasing his father? That was part of the evidence I put together as I came to my conclusion that his sudden, vocal, very obvious piety was not a lifelong religious devotion and his atheism just some meaningless words he once said to look good in intellectual society.

How strong an attachment he might have had to freethinking vs. the consolations of religion in extremis we'll never know, but everything he did and said screams "a man with an audience" at me. Multiple audiences. And I am absolutely sure that even once there was no hope of a royal pardon, in the very last seconds, he was trying to make sure he did his family proud, both in piety and in courage. (Somewhere in my fic drafts folder is an attempt at a depiction of all the many complex thoughts, feelings, and coping strategies I think were going through Katte's head in his last days.)