Some processing thoughts:

zcat log.gz | grep ^1 | tail -n +200000 > log-locked

octave:

  a=load("log-locked");
  len=size(a,1)
  t=1:10000;
  keith=a(:,3);
  calib=a(1,4)
  dac=a(:,5);
  adc=a(:,6);
  meas=-(dac - calib * adc);
  plot(keith(t),meas(t))   # should be linear

  p = polyfit(keith, meas, 1)
  plot(t,keith(t) * p(1) + p(2),t,meas(t))   # should match

  t=1:len;
  plot(t,keith(t) * p(1) + p(2) - meas(t))   # absolute error (units=dac)
  axis([0 len -1 1])

Range is something like +- 0.5 over the entire range (of "DAC values")
This gives log(1024 / 1.0) / log(2) = 10 bits
No good!
Now let's convert the DAC values to their more-accurate value using the lookup table

  lookup=load("../../../firmware/lookup.inc");
  size(lookup)
  meas=-(lookup(dac + 1)/64 - calib * adc);
  p = polyfit(keith, meas, 1)
  t=1:len;

  plot(t,keith(t) * p(1) + p(2) - meas(t))   # absolute error (units=dac)
  axis([0 len -0.3 0.3])

Now closer to +- 0.05
This gives log(1024 / 0.1) / log(2) = 13.3 bits