First, welcome. This place has a wealth of information and people are generally quick to respond (as long as Yahoo is cooperating. . .)
Looking quickly at you ink descriptor file it is easy to see what the problem is (even without looking at your measurement graph).
As it is now, your profile essentially printing like the black channel in the ink separation page printed in Calibration mode with the ink limit set to 35. The hardware spits ink onto the paper in direct proportion to the input from the file, but causes the density to increase too quickly for real world photographic uses. That is the essential problem calibrating and profiling is attempting to control.
For the linearization function to be successful you need to be able to print the 21-step target with settings that control the dot gain increase and allow some more separation between each 5% patch.
The easiest way to do that is with the GRAY_HILIGHT= and GRAY-SHADOW= settings.
Even increasing them to the default of 4 (right now they are set to 0) might be enough, but try setting them to 6 for the highlight and 10 for the shadow. You could also increase the GRAY_GAMMA setting to 1.2-1.6 to try to open up the tones the initial 21-step target.
(If my response from earlier today ever shows up you'll see that i just told you to enter some numbers into the GRAY_CURVE= setting. If you do that you will need to leave you setting just as you have them above, and delete the linearize= line.)
Hope that helps,
Richard Boutwell