Misc: How many stars are there on the U S flag?

Questions

In Lord Valentine's Castle, Valentine's profession until his memory returns.?

Director of the FBI who lived from 1895-1972.?

The first name of the American statistician who established the Gallup poll?

American dramatist whose plays include Death of a Salesman and The Crucible.?

American psychologist known for his experiments with hallucinogenics in the 60s?