I dont have time to play xbox everyday, usually a few times a week, thats why I have not updated. Right now I am in the Queen Hive (Gears 2) and Marcus' dad mentioned something about sinking the main city to flood out the Locust.
1. They leave a lot vague about Marcus's dad in the first but by the end of the third, all will be revealed. Same for the reason why Marcus was in prison when the first game begins.
2. See answer #1
3. The first game was global but only told the story of a few participants in a larger war. Your whole mission was to get a device into the heart of the locust tunnels so that you could map them. Unfortunately, the tunnels were so immense and expansive, they barely accomplished anything. The Cog even destroyed their own cities (with the Hammer of Dawn) in an attempt to stop the Locusts. By the end of the second game, there's only one city left that is safe for humans...