Cool Gray 5 should be set to the spot color in Illustrator or 15% C, 9% M, 8% Y, 22% K. Period. If the output does not match cool gray 5 you need to recreate your profile or create a custom color in versaworks using a pantone swatchbook. You shouldn't be adjusting color levels in illustrator to achieve a color, because the problem is not your file -- it is your profile.