Yes, the auto brakes are off during taxi. Otherwise, they would be constantly slowing down the A/C, negating the objective of taxying.
Towards the end of the landing roll, the ABRK would be disengaged by the pilot at low speed, in order to prevent a locked wheel situation once the anti-skid (a.k.a ABS) deactivates (technical low-speed threshold for that). Actually 30 knots is about the right moment, after which you'd assume normal pedal braking.
The answer to your question is pretty useless: the distance depends on how hard you press on the brake pedals, and what is the surface friction available. If I pressed the pedals to the metal, the brakes lock giving max effectiveness on a dry surface, and we'd skid to a stop inside 30 meters. Possibly even sooner - and trash all the 4 tyres.