LOST questions that still bug me

When LOST wrapped up last year, I planned to start re-watching the series from beginning to end. In due course I started with Season 1...and barely finished it about six weeks ago...maybe a little less.

Today I finished Season 2, so I guess I'm picking up a little momentum. All this free time being laid off, I guess.

It's been good to go back and rewatch. I'm getting close to my favorite extended period of the entire series, which is from the middle (or so) of Season 3 to the end of Season 4. Much of Season 5 was good, too.

Anyways, I've had a post about this before, but these are unanswered LOST questions that still rankle:

• How did DHARMA know about the Island? Why were they there?
• Why didn't the "headquarters" for DHARMA know their island personnel had been "purged"? (i.e., why was food still dropped on the Island?)
• Why are “The Others” on the island? Who or what is behind them, as they seemed to have significant resources?
• I suppose they may have just been the protectors of the Island, to help Richard and Jacob, but that seems too simplistic.
• Who built the big statue?
• Why was Libby in the crazy house? Did she know Hurley from there, or was she too drugged up to have any clue?
• Was there ulterior motive in Libby letting Desmond use her boat in the race around the world? Or was she just kindhearted? 
• How did Penny know what to have her two dudes look for (season 2 finale)?
• In season 2, why/how was Walt appearing to Shannon? Was it actually him?

That's it for now...Actually not as many as I thought, but chances are I'll be adding to this post as I keep watching.