Digital BW, The Print

I'm on Win98se
An old Sony (Trinitron).
Windows default Gamma 2.2
White Point Hardware 6500k or Custom (if I choose the 'measure' 
button & warm the centre square slightly)

I use Adobe Gamma (either the control panel or the wizard) to set up 
my monitor. 

With the control panel I select to view the single gamma only. Using 
the patterned square with the plain little square within it - i use 
the slider carefully until the middle square fades into the larger 
one. Sitting back a little with my eyes squinted/out of focus.

Or, using the wizard, I set my contrast and then brightness until the 
middle square is "as dark as possible but not black" - still 
distinguishable from its surrounding.

All as per instruction.

Now if I view (under the same light) a 21 step tablet the 95/100% 
almost meld into one another Pretty close to being indistinguishable 
which is not right. 
Why the discrepancy ? Other than expensive calibration equipment how 
can I improve my "calibration" methods.