How can I convert a Survival mode save back to a normal save?
You can switch a survival game to a different difficulty the same way you normally change the difficulty, through the Settings -> Gameplay menu. I don't know if this was missing when the beta was released yesterday, but I just tested it by loading a save, switching it to survival, and then switching it back.
Lowering the difficulty from survival is a one-way change, you cannot lower the difficulty and then raise it back to survival, as indicated by the warning you get when you try to lower the difficulty:
