set specular, 0
alone should be enough to do the job if all you want to do is turn off specular lighting -- you can ignore all those other spec_* settings.
However, for a more matte appearance I’d be more inclined to try:
set specular_intensity, 0.2
# and perhaps
# in order to lessen problems with color saturation.
This email (including any attachments) may contain material that is confidential and privileged and is for the sole use of the intended recipient. Any review, reliance or distribution by others or forwarding without express permission is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies. Exelixis, Inc. reserves the right, to the extent and under circumstances permitted by applicable law, to retain, monitor and intercept e-mail messages to and from its systems.