My take on a few of your questions:
1. Yes, Osborn is sort of the Luthor of the Marvel U. Though I would argue that he's more powerful than Luthor was even when Lex was President. Right now Osborn has his fingers in just about everything. However, there are hints from the upcoming "Seige" storyline that there might be someone more powerful behind the scenes.
2. Milestone is a part of DC universe proper. I'm not sure if Archie is. However, despite a guest spot in the Dwayne McDuffie's closing run on the JLA, and some guest spots in Brave and the Bold, most of the Milestone characters are going to be put back on the shelf, at least for the foreseeable future. The only Milestone character that is going to get some play is Static, and he has been added to the Teen Titans after debuting in Terror Titans. DC is going back and issuing trades of the old Milestone work. I have both the Static and Icon trades. I heard that McDuffie will also get to wrap up the original Icon storyline.
3. Dick is the new Batman. The Nightwing name is now being used by Chris Kent, the adopted son of Superman and Lois Lane in one of the Superman books. They've bought back the team of Flamebird and Nightwing. Along with Mon-El and Supergirl they are watching after Earth while Supes is on New Krypton.
4. There is a New Krypton; the inhabitants were from the bottle city Kandor. Personally I liked the NK arc, it added something different to the Superman universe. It gives Superman a whole new list of problems and divided loyalties to contend with. Plus it opens up the potential for more adversaries.
7. Dark Reign is the big event for Marvel after Secret Invasion. Most of the books with the DR title over them are supposed to be related to the big storyline, though its mainly just a ploy to sell more books IMO. Though some of the sidestories are more interesting than what's happening in Dark Avengers, which I'm assuming is the main DR book.