To answer your first question about qidf/profiles/curves: Think of QTR curves as very accurate media settings for the exact paper and ink and printer used to make them. You can then make an ICC profile using those media settings for soft proofing in Photoshop (which is not as helpful as you think it might be). Printing with color management and QTR is easier through OS X either through Photoshop or PrintTool, but isn't really advised, at least not my me personally. It is a little more complicated with the QTRgui in that you need to convert the file to the ICC profile in Photoshop, then save and print through the QTRgui.
About the need to print with ICC profiles and application managed color matching: In many cases printing with color management will block the shadows up too severely, and I tend to like the linear tonal distribution on gloss papers. But, I do need to introduce a little shadow compression with matte papers so I use a combination of the color picker/info pallet and a printed step wedge to create a final printing adjustment curve on an image by image basis. That is similar to what Paul does with his QTR to GG2.2 curve, but I customize mine to each image based on the actual printed step wedge and the K% values in the file.
Hope that helps,
Richard Boutwell
http://www.richardboutwell.com/