Hard to give an exact length for Rage's story. It could be short and to the point or long and filled with twists and turns. A lot depends on how much background, character development, and events are included.
Well, Vegeta would be a likely character. He might be initially suspicious of the female Goku. Maybe he thinks she's a threat or just can't believe there's another Goku - like being. He could be there to add some comical moments as he tries to understand the situation.
No. Ken's rage might be just one aspect of the story. There could be other characters' emotions, motives, and events that are not related to his rage but are essential parts of the full story.
Yes. If the story is a character study specifically focused on Ken and his rage is the driving force behind all the events and character development in the story, then it can cover the full story.
Goku's depression in fanfiction could stem from his identity crisis. He is often seen as a powerful Saiyan warrior, but what if he starts to question his purpose? Maybe he realizes that his constant battles are causing destruction and harm to the planets he is supposed to protect. This self - reflection can lead to feelings of depression.
Rage comics can be copyrighted. If the creator of a specific rage comic has taken steps to register it for copyright protection, then it is copyrighted.
Well, that depends. Maybe you could provide more information like the plot, characters, or any unique features to determine if it's the Spartan Rage comic you're thinking of.
It could be a female Namekian. Since Namekians are also very strong and have their own unique culture, a female Namekian could catch Goku's eye. They might bond over their mutual respect for life and their experiences with fighting powerful foes.