Well, never got any reply on how to interpret those duty cycle numbers, but here is the update.

After overall work of:
Replacing coolant sensor (probably OK originally)
Replacing plugs
Replacing O2 sensor
Repairing several vacuum leaks
Adjusting mixture by feel more towards lean

I passed my retest.

The numbers:
At 15 MPH CO was 0.35% (down from 8.48% on prior test)
At 25 MPH CO was 0.16% (down from 7.94% on prior test)
At 15 MPH HC was 123 PPM (down from 339 PPM on prior test)
At 25 MPH HC was 59 PPM (down from 322 PPM on prior test)
At 15 MPH NO was 915 PPM (up from 234 PPM on prior test)
At 25 MPH NO was 545 PPM (up from 160 PPM on prior test)
At 15 MPH O2% was 0.4% (up from 0.0% on prior test)
At 25 MPH O2% was 0.1% (up from 0.0% on prior test)
At 15 MPH CO2% was 14.6% (up from 9.6% on prior test)
At 25 MPH CO2% was 15.0% (up from 10% on prior test)


The new numbers are much better, of course, but the low speed HC and NO numbers were a squeaker to pass. My 123 PPM HC just squeaked by under the 126 limit, and my 915 NO wasn't much better against the 1097 limit.