Maybe. But if they did it was never in the open. I like to think that they didn't.
If he didn't he should have.
no, you have the question wrong: "Do you think Festus and Miss Kitty ever had sex?"
Why, no. It's not as if she was running a bawdy-house. In the Wild West. Where there were few women. And lots of lonely men. With money. Did I mention she was a ginger?