Thorfinn x Canute fanfiction often explores a complex relationship. It can show their different personalities clashing and meshing. Thorfinn, with his warrior background, and Canute, the king, have a lot of potential for interesting interactions in fan - made stories. Their relationship might be one of mutual respect, or it could be filled with tension as they have different goals and outlooks on life.
A less common but still interesting trope is the 'swap of roles' in Thorfinn x Canute fanfiction. For instance, Thorfinn might find himself in a position of political power for a while, while Canute has to rely on his combat skills. This trope can lead to a lot of interesting character exploration and development as they both have to adapt to new situations outside of their comfort zones.
I think there's a chance. The manga is full of surprises, and a new conflict that involves Thorfinn fighting could arise to add more excitement and drama to the story.
Thorfinn does fight again. The manga develops his character through various combat situations, each presenting different obstacles and opportunities for growth.
King Canute was a real historical figure. He was a king who ruled over parts of England, Denmark, and Norway. In the story, he is portrayed as a king who wanted to teach his subjects a lesson about his power not being limitless.