Hi!
1) 29 and 30th I think should be fine days to go. They will not be heavily crowded, but they wont be non-existent.
2) Fast Lane is always worth it. Even if you spot a 10 minute line on dragster, it still helps!
3) Wait to buy fast lane till you are AT the park. That will give you a general idea of if you will need one or not!
Hope this helps!