I am trying to use dd to copy a tape made by amanda to a temp spot on the HDD, but I am having great difficulty. When I try to use dd, it will only copy one file at a time then stop, no matter what I do. As far as I know, dd should just take the entire tape from beginning to end. . .

dd does one tape file at a time, which yes, is what amanda writes.
In order to do what you're trying to do you just need to write a
short script to put your dd into a loop.

-Mitch