in "The Black Cat," how does Poe develop the character of the narrator to create suspense and tension?

The narrator of Edgar Allan Poe's "The Black Cat" gradually changes from a man of sane, congenial nature to a psychopathic man.
In the beginning of the story, the narrator seems quite genial in nature:

From my infancy I was noted for the docility and humanity of my disposition. My tenderness of heart was even so conspicuous as to make me the jest of my companions.

As a young man, the narrator marries young and finds a wife who makes him happy because she possesses a disposition "not uncongenial with my own." Because she notices how much her husband loves animals, she takes the opportunity to procure several pets for him. He prefers a large and "sagacious" black cat over the others, and Pluto, as he names it, becomes his favorite pet—even a playmate. For several years this cat follows him about the house.But, when the narrator begins to drink, his disposition alters and he becomes impaired in empathy. While he remains rational, the narrator loses any affection for his pets; in fact, he is abusive and neglectful towards them. He also turns his abuse upon his wife. Still, he restrains himself for awhile around his favorite pet, Pluto. But, one evening when the cat bites him slightly, the drunken narrator describes a flight of his soul from his body:

...a more than fiendish malevolence, gin-nurtured, thrilled every fiber of my frame.

Then, with his pocket-knife, he cuts one of the cat's eyes from the socket. The horror of this act certainly creates suspense and tension in the narrative as the reader wonders what may occur next.
After some time, Pluto recovers, but he flees in terror from the narrator whenever the man gets near him. The narrator states that he feels himself overcome with "the spirit of perverseness." He feels a strong urge to do wrong for "wrong's sake only"; so, one morning he slips a noose around the cat's neck and hangs it.After his house burns and the cat is found somehow inside the house, although he has hanged it in the garden, the narrator begins to feel not remorse, but some regret for having killed Pluto. Because of this regret, he finds a cat that resembles his first pet. However, he begins to dread the new cat when he realizes that it, too, is missing an eye. At this point, the narrator begins to descend into the darkness of irrationality, and tension is generated in the story.
One day as the narrator goes down the steep stairs of his cellar, the cat follows him and nearly trips him. This act "exasperated [him] to madness." He lifts an ax to strike a blow at the cat, but, instead, his wife arrests his swing. Flying into a rage "more than demoniacal," the narrator embeds the ax in the brain of his wife. Once this happens, the narrator acts with "entire deliberation." Like a psychopath, he remains rational and very aware of his actions: "Many projects entered my mind." The narrator finally decides to bury his wife in a projected area where a false chimney or fireplace may have been, but has been filled up. After having displaced the bricks and placing the corpse inside, he walls her in, but later comments, "The guilt of my dark deed disturbed me but little."
Here, then, the tension definitely increases as the reader wonders what actions are next. When the police come to his house, the narrator "felt no embarrassment whatever." In fact, when the officers can find no evidence of wrongdoing, the narrator observes,

The glee in my heart was too strong to be restrained. I burned to say a word, by way of triumph, and to render doubly sure their assurance of my guiltlessness.

In his boldness, then, which is typical of a psychopath, he raps upon the brickwork where his wife's corpse stands. The tension increases here until "a howl, a wailing shriek" issues from behind the wall. For there atop the wife's head sits the

...hideous beast whose craft had seduced me into murder and whose informing voice had consigned me to the hangman. I had walled the monster up within the tomb!

Still feeling no remorse for his behavior, the narrator exhibits the antisocial behavior of a psychopath in this suspenseful and tense narrative.