Not sure what's happening to your profiles, but you did not answer as to whether you had indeed calibrated the paper. If you have, try the canned HP profile for the paper instead of your custom one and see if there is any difference.
As far as printing landscapeon a roll, I do it all the time. In the Features Tab of the 3100 driver, under Roll Options, check the Auto Rotate box. That should do the trick.
Good luck,
Jim