Digital BW, The Print

First let me admit that I haven't read through your procedure yet. 
That said, it would probably be best to always compare the printed 
patches to some kind of "standard", just like you do when making a 
scanner based color ICC profile. Those use an IT8 target scanned 
along with the printed target. Since the IT8 target has a standard 
layout (until you get into the extended IT8 formats), would it make 
sense to find a value(s) on the chart to set the scanner too? Those 
also have the advantage of having "known" values that you can use to 
compare the printed target too. Maybe it's time to make and measure a 
bunch of 21 step patches to use as a reference, just not sure what 
paper should be used.