Since I don't have access to the details of this novel, it's difficult to determine exactly who the king of the cave is. It could be a protagonist who has a significant role to play in the paradise - like life described in the novel. It might be a figure that the whole plot revolves around, perhaps with a mysterious origin or a grand mission.
In the context of this novel, 'paradise life' might refer to a state of existence that is far from the ordinary. It could involve having extraordinary experiences, being in a place of great beauty and harmony. For the king of the cave, it might mean having supreme power, living in a utopian - like environment, perhaps with no strife or suffering. It could also imply a spiritual or emotional fulfillment that is rare in normal life. This kind of life could be a central theme in the novel, driving the plot and the actions of the characters.
Partly. While the main themes and overall plot might be rooted in real experiences, some elements could have been fictionalized or dramatized for cinematic effect.
There's no definite information about the exact location of the cave in the story. It could be anywhere in the Arthurian landscape, perhaps in a forested area or near a magical lake.