The warm is indeed linear. The neutral and cool are too light.
You may have just not installed the curve (the one that you did as the 2nd lin) before you printed the target?
Anyway, all you need to do is error correct the measurements from 3rd-lin cool and neutral and then use these corrected measurements to linearize the cool and neutral curves that you printed these 3rd-lin targets with.
That should do the trick. There may be some problems with workflow and notes that happened with the cool and neutral curves.
Related to darkness, these are linear curves with very dark L* values in the shadows.
I suggest taking the neutral validation corrected .txt file and (instead of selecting it with a .quad and dragging over QTR-Create-ICC) drag just it over the QTR-Create-ICC-RGB. Put the resulting profile in Applications>Piezography>ICCS>SoftProof and then sxftproof with this profile with “Preserve RGB Numbers” turned on.
This will simulate the exact contrast of the print on your monitor.