Well, I can't help you with 1., and 3. is something all DMs sacrifice unless they're working in pairs. However...

If you're not confident in worldbuilding, I'd say that [i]if you ever try GMing again[/i], you should look at Paizo's adventure paths for Pathfinder. They lay out whole campaigns for you to use, and if you're playing with people who haven't played that campaign before, they'll be in for a pretty good story. A lot of them are really well written, and they dabble in very different genres. You get things from Fantasy Horror to Fantasy with sci-fi elements to traditional "Let's loot the dungeon!" fantasy.

I totally understand 3., though. I love to be surprised when I play tabletop games. That's why I've always preferred to be a player in tabletop games.