I didn't see him as a magical black person trope. Yes, he gave some guidance where guidance was needed, but he wasn't exactly a faultless character himself. He'd committed plenty of crimes in the past, and though he's trying to clean up his act, he only just started trying to be a better person at the end of the story. And his seemingly good advice is indirectly responsible for getting himself killed, though he couldn't have known that.
Anyway, I liked this story okay. The whole thing was depressing, but I liked the body of it nonetheless. The dog especially gave me chills--not so much the fact that it was possibly a ghost, but because the family just left it to drag its ass around the house and that the dog still seemed pretty happy despite that. And if they mom was going to put the dog's toys in the basement to get it out of the way, why didn't she just bring the DOG to the basement too? Otherwise the end of that is pretty predictable. Then again, she wasn't exactly compassionate, so she was probably ready to off the dog anyway.
What I didn't like was the ending. If the dog is just a figment, then laughing at the man's death will do nothing but drive a bigger rift between himself and his mom, and leave him with even more guilt. If the dog is a ghost, then, sure, he'll have the guy hanging around. But what good will that do? his mom won't be able to see him so he can't exactly mediate. Sure, maybe he can get advice from him, but look where his last advice gained him. And what if the haunting keeps him from moving on to a happy afterlife and he's damned him here forever? No matter how I look at the ending it just isn't satisfying.