Very thoughtful and insightful review!
I rate "Mean Streets" second only to "Raging Bull" among Scorsese's works. Intriguing premise (would-be Mafioso as "moral man" in the mean streets of NYC), perfectly realized in Harvey Keitel's finest role. And DeNiro's second-best (after "Bull"). A uniquely creative, intellectually and morally challenging film.

Glad you mentioned the sound track, which works brilliantly and with terrific precision. The pinnacle: Charlie putting on his new monogrammed shirt to The Chantels' "I Love You So." Brilliant, but one of many such lapidary moments, such as The Paragons' "Florence" when they're on their way to the pool room; The Chips' "Rubber Biscuit" in that drunk scene that you mentioned; plus the inimital "Be My Baby" over the opening credits--a perfect song for Charlie's desire to be accepted as a "moral man."