Hi Attila, I have a HP lp2475w, I hope I can be of some help.
As to 1), I don't quite see what you mean. You can enable DDC through the on-screen menu, press Menu, Management, DDC/CI Support, press On, but that's the default so it should be On already. But still, I calibrate with Eye-One Display 2, it doesn't quite work like that. You set the values for Brightness, Contrast and R, G, B values through the on-screen menu or, much easier, the HP Display Assistant. The Eye-Match software helps you adjust the settings as closely as possible to desired values, then measures the patches the monitor displays, and then builds a profile on what it measures to correct to desired values. The profile doesn't actually adjust the values for Brightness, Contrast and RGB values.
As to 2), I noticed something that others have also noticed (check Dpreview forums) - unfortunately the screen isn't quite uniform, I don't know whether you noticed. Apparently this is not uncommon for screens of this type, but it's a bummer nonetheless. The right side of the screen is slightly but visibly warmer (redder) than the left side of the screen. So I calibrate a 'sweetspot' just left of the centre where I usually check my photos in Photoshop, the right side is where the menu etc. are. However you calibrate, there will always be an area to the left or to the right that won't match your Eizo.
Also, you may have noticed that the factory default settings for the RGB values are set to 255, 255, 255. This is way too much. You can adjust the Brightness down to 20 or so, but I noticed that that gives too much red in the highlights. If you first adjust the values for RGB in the on-screen menu or in HP Display Assistant to more moderate values such as 180, 180, 180 with Brightness to a relatively higher value e.g. 70 or 80, and start your calibration from there, you get a much smoother result.
Hope this helps,