RaceFail '09: God, where to start. Well, it did start as a cultural appropriation debate, became a racism debate, and then escalated and derailed into something spectacularly ugly in which various S/F editors and some writers responded to criticism by threatening the lj people who made it and by outing them (i.e. reveal their real life names). These two (http://coffeeandink.livejournal.com/901816.html)
posts (http://linaerys.livejournal.com/663811.html) are as good a summary of the most recent developments as any; if you want to know more, as I said, ryda_wrong keeps collecting links in her journal and has done from the start.

Horace first showed up in Ben's origin episode, The Man Behind the Curtain; he and the now absent Olivia met Roger Linus & Roger's wife Emily in Portland, giving them a lift to the next hospital, only they didn't reach it as Emily gave birth to Ben in Horace's car and died of it. In the next flashback, we saw Horace and Olivia on the island, when Roger arrived because Horace had promised him a job in the Dharma Initiative, and likely as not was the only friend Roger, who by then was a hopeless drunk, had left. (Ben at this point was around 11 years old, just so you know where we are in the timeline.) In the last flashback, when the Purge happened and Ben after killing his father returned to the village, Horace's corpse was the only one he stopped at in order to close Horace's eyes. The next episode we saw him in was a season later, Cabin Fever, a Locke episode; when Locke, Ben and Hurley were searching for Jacob's cabin, Locke had a dream of Horace, in which Horace ("I'm not making any sense, am I? That's because I've been dead for twelve years") told him where to look.

I'm pretty sure Miles is the Asian baby we see at the start of this season, in the Dharma flashback scene with the instructor shooting his videos, yes.

Quadrangle of doom: by now, yes, but it started out as a triangle between Sawyer, Jack and Kate way back in season 1, and I found it a boring one even then.

The pilot's name is Frank Lapidus.

The Butterfly Effect: hm, could be an interesting option as well, but as you said, not if it just results, in say, them returning to the present to find each and everyone who died on the show alive as a happy ending. You could be right about Amy's child changing things, though, because he can't be Miles (being Caucasian), he's male so can't be Charlotte, either, and Ben was born a decade earlier and elsewhere as we've already seen on the show. So as of now, I have no idea who that child could be in the present as we know it. By and large, though, I think they'll go with 1), and whatever they do in the past will contribute to creating the familiar present.