Well, Bakugo might scoff at first. He'd probably think Batman is too brooding and not as straightforward as he likes his heroes. But then as he reads more of the fanfiction, he might grudgingly admit that Batman's detective skills are cool. Deku, on the other hand, would be super interested. He'd be analyzing every move Batman makes in the fanfiction, taking notes in his head about Batman's strategies and how they could be applied in his own hero work. Uraraka would be more focused on the relationships in the fanfiction. She'd be all 'aww' at the cute moments and feel for the characters when they're in trouble.
His aggression might become more unhinged. Without the moral compass of the hero side, he could be more willing to use excessive force. He'd still be competitive, but now it would be against heroes instead of his fellow hero trainees.
Bakugou could use his words. He might tell Deku that he believes in him. For example, he could say 'Deku, you may be a nerd but you're a strong nerd.' It's a backhanded compliment but it shows he has faith in Deku.
Definitely not. Bakugou is still alive and kicking in the manga. The creators have kept him around to drive the story forward and engage the readers with his dynamic personality and actions.
Kirishima would probably support Bakugou. He respects Bakugou's strength and no - nonsense attitude. He also doesn't like Mineta's pervy behavior, so he might think that Mineta deserved it. Kirishima would see Bakugou's action as a way to keep the class in line.
Several characters have met their demise in the MHA manga, but it's a bit complex to list them all precisely. Some of the notable ones include [mention specific characters if known].
I think it's hard to say for sure. There are a few characters who could potentially be the traitor, and it's all part of the mystery and suspense of the story.
The relationship could start with hatred. Bakugou may initially be enraged that Deku has become a villain. But as time passes, he starts to see the reasons behind Deku's transformation, which could lead to a more complex relationship.