Acute means to have a good sense of hearing or smelling. This is important to the story because when Edgar Allan Poe creates suspense when he says he hears all things on heaven and earth. Him saying that he has a acute sense of hearing makes you believe he can hear everything.
When he says the old man did that vexed him but his evil eye. This shows how much the evil eye actually bothered him. When he uses vexed it creates this suspense so we feel how he feels.
The again and again is when Edgar Allan Poe sneaks into the old mans several nights until he finally did his deed.In the text it says "upon the eighth night I was more than usually cautious in opening the door.