[spoiler]I think the older guy was pretty much like, Oskar. Eli, befriended him when he was young, and he just got old and out lived his usefulness. As for the drinking scene, yeah, I felt that it alluded to abuse as well. But I think it was mostly just another scene to show us how neglected, Oskar is.
As for the vagina thing, I kind of figured that whole castrated thing. I mean, she keeps saying how she isn't a girl throughout the movie.[/spoiler]
I just love the movie. There is so much going on it, little hints here in there, letting you know more about a character. It's just awesome. definitely my favorite movie of last year. And one of my favorites ever.