1) It seems as though the home, while a "space of innocence" at the beginning of films, is broken, flawed and or ill-suited for the needs of our hero. It is a "space of innocence" because the hero doesn't yet know how to break out, how to live in the real world. However by no means is this home a good place. Consider Cinderella's home with her step mother and sisters, Ariel's male dominated sea palace or Belle's boring village life. However, the home can also be a place of peace that is disrupted; this disruption sends the hero on his quest. Consider Simba in The Lion King, whose idyllic life is disrupted when his father is killed. The idea of a safe, welcome or loving home is often what the hero strives to return to. And it is often at the end of the film that the hero is given an upgraded home or "space of innocence". In Aladdin, the beggar becomes wealthy and ends up with the princess, In The Lion King, Simba becomes King and in Cindarella, Cinderella leaves her abusive step-family and moves in with the Prince.
2) Melodrama often features a poor or disadvantaged hero and a greedy, if not wealthy villain. Unlike in post-modernist works, where the hero must fight his own internal demons, the hero in a melodrama often wins by stroke of luck. This means there are often "nick of time" scenarios; The damsel in distress is rescued from the train tracks, right before the train crushes her. Because the hero faces external struggle, that struggle often manifests itself in time-sensitive situations. The resulting success gives this "nick of time" feeling. What helps to set up the "nick of time" feeling is the "too late" scenario. Often before the hero can win out in the last second, he faces tragedy when he is too late fix the problem. This situation can prove to be a crucible for the hero, though eventually he redoubles the efforts to succeed. The "too late" and "nick of time" provide a symbiotic relationship. Without the "too late", the "nick of time" isn't has trying and suspenseful for the viewer/reader and without the "nick of time", there is no victory and the story ends without a satisfying resolution. The first example that came to mind was The Dark Knight, Christopher Nolan's 2008 blockbuster film. Though it contains both post-modernist and melodramatic elements. the film features the "too late" when Batman is unable to save Rachel from the Joker's bomb. However, later in the film, Batman is able to save Commissioner Gordon and his family "in the nick of time" against villain Two Face. Having experienced a shocking loss, the view is even more satisfied by the happier resolution at the end of the film.
3) When I first attempted to answer this question, I was certain that a lack of pathos and action prevented comedies from winning the Best Picture Oscar. However, after looking at a list of Best Picture winners for context, I realized that the answer isn't that easy. I had working under the assumption that the award was given to critically acclaimed dramas and character studies, basing my assumption off of wins by The Hurt Locker and The King's Speech in recent years. However, after some research the list is more diverse than originally thought. Included among the winners are Argo - which provided plenty of humor, Annie Hall - Woody Allen's nerotic and Chicago, a musical. I do agree that pathos is required for a film to win Best Picture. But maybe it isn't that comedies don't have the required pathos for Best Picture, perhaps most comedies are written to supply the most laughs or revenue instead of a mix of humor, pathos and action. Off the top of my head I can think of two films that fulfill those requirements; both are mandatory viewings in Intro to Film classes: The Graduate and A Fish Called Wanda. In addition, there seem to be other criteria for Best Picture besides an inclusion of pathos and action. Big Budget films have mostly been ignored; the Academy often has focused on smaller, more artist driven films, at least recently.