Does Joker know he is in a comic?

I think he doesn't. The Joker's character is often depicted as being so immersed in his chaotic world that he probably doesn't have that kind of self-awareness.

It's hard to say for sure. Sometimes it seems like he might have an inkling, but it's never explicitly shown.

Well, it's ambiguous. In some interpretations, Joker might be oblivious to being in a comic world. But in others, there are hints that he might have some awareness, though it's not clear-cut.

In most versions, Joker doesn't seem to have that awareness. His focus is on causing mayhem and chaos without considering the meta aspect of being in a comic book. It's part of what makes his character so wild and unhinged.

Yes, Deadpool is aware that he's in a comic book. He often breaks the fourth wall and makes references to it.

Well, Deadpool's awareness could come from his constant breaking of the fourth wall and his unique meta-awareness. He just seems to have that crazy ability to realize he's in a comic.

Well, sometimes it seems like he does. He often breaks the fourth wall and makes comments that suggest he's aware of his fictional status.

No, Batman usually doesn't kill the Joker. His moral code prevents him from taking a life, even that of his arch-nemesis.

Sure, Deadpool frequently acknowledges being in a comic. This awareness is a defining trait that adds to his humor and unconventional nature. It allows for meta-commentary and breaks the fourth wall.

It's hard to say for sure. Maybe he does, maybe he doesn't. The comic creators haven't made it clear.