sound to me like the master cylinder seals have failed, except for brake fluid leaks or boiling, the master cylinder is the only thing to allow the pedal to travel so far, if the servo has gone (& not the master cylinder) the pedal should be hard to press & at the top, its possible the master clinder has leaked fluid into the servo & rotted the diaphram (but ive never come accross it) start with the cylinder. also if the servo is leaking that bad, you must have a really poor idle