I’m so glad this Ed gets a happy ending. Now him and McQueen can be together happily. ...

I'm not too sure either. My only guess is that he doesn't want ANY friends from the mafia so he doesn't get mixed up in all that.
And since he stopped visiting Chang to talk about other "work options" (mob jobs), he would rather not visit at all so he can keep his life separate from all that.

Also that isn't Chang's brother. That kid is the kid of a mafia boss that Chang does business with. He just likes to hang around Chang and Ed to avoid his parents.