Montresor might be sick due to the inner conflict and remorse. His conscience could have finally caught up with him, causing physical symptoms. Another possibility is that the intensity of the emotions during the events at the end of the story overwhelmed his system.
In the end, Montresor successfully achieves his revenge by walling up Fortunato alive.
Montresor is telling this story to an unnamed person. We don't get a clear identification of who this person is in the story. It could be someone he trusts, or perhaps he's just unburdening his conscience to a random listener.
Maybe he wants to get something off his chest or seek some kind of validation.
The recipient of Montresor's tale is ambiguous. It might be someone he considers a confidant, or it could be a symbolic act of sharing his burden with an imagined audience to unburden his conscience.
There's no clear indication in the text about who Montresor is telling the story to. It leaves it up to the reader's imagination.
It's a real story because it was drawn from the personal experiences of Kumail Nanjiani. His relationship with his wife, the cultural clashes they faced, and her illness were all real things that they went through, and these elements are what make the movie a real - life story.
One possibility is that he could be telling his story to a priest. In the context of seeking absolution, Montresor might be confessing his dark deed. Priests are often the recipients of confessions, and Montresor, burdened by his conscience perhaps, could be unburdening himself to a man of God.
Montresor is vengeful and calculating. He plans his revenge on Fortunato meticulously.
It could be to a close friend or confidant, someone he trusts to listen and understand.
The fact that it's a real - life love story. It shows that love can overcome cultural barriers. Kumail and Emily's relationship was tested by her illness and cultural differences, but they made it through.