Most likely its describing Old Lady Chong"s finger. "Like a dead person, like an old peach I once found in the back of the refrigerator. It should be touch since its describing Old lady Chongs age.
Usher's madness begins to increase because he can hear the sound of Madeline below.
Even though his sister is buried in the basement, he can constantly hear her scratching her coffin. He was tortured by these sounds until the protagonist came to visit him so he could share his troubles with him. Usher is afraid of his 'undead' sister and of dying himself, which is why he grows crazier and crazier by the day, until he is finally killed by his own sister in the end.
