The movie Ronin indeed takes inspiration from the graphic novel. They share core elements and themes, but the movie might have made some adaptations for the big screen.
The shadow of Ronin was Min Zaizhi, the boss of Gao Haili, who was played by Xiuzhi. He was also the person with the code name M and was also the mole in the Blue House. He had been helping the villain company with various missions.
The 47 Ronin story has indeed been made into a comic book. It typically features detailed illustrations and a narrative that stays true to the original legend, while adding some creative elements for visual appeal.
To some extent, it's true. However, like many historical tales passed down through generations, there are likely exaggerations and additions to make the story more dramatic and engaging.