The actual runway length IS
is used to determine V1. However, it is only a baseline V1. Other factors, such as runway slope, wind, etc., will influence V1.
Of course, for the purpose of this topic, the number in the flip books are all based on weights, as the maximum weights for the flight (which includes maximum takeoff weight for a given runway, 2nd segment climb, enroute driftdown, and maximum landing weight) are figured out during the pre-flight planning stage. And to answer your second question, ASDA is NOT used for takeoff distance, but rather the takeoff distance required is 115% that of the takeoff runway distance available where the plane must reach a minimum of 35 feet above the runway plane.
That's with U.S. regs. Other counties may vary.
[Edited 2009-02-08 14:46:12]
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.