Excellent first effort on Medium! If two or three exclamation points in a row didn't seem so amateur, I'd add about four.

The only thing I would change (since you asked) is in the last paragraph. I would dot it like this: "Tellin' the truth ain't no sin, bro." He gazed off into his past. [or something] "I don't know why I go...." A reader without much time to devote to this story will otherwise run the two sentences together and lose the meaning of both.