I don't know about those first two things, but the screen resolution thing is simple. Once you change/update XF86Config-4 you will need to quit kdm and restart it. I don't know a "safe" way to stop it, so I just do 'ps -ax' and find the pid and then 'kill pid#'. Then just restart kdm again with 'kdm'. Thats how I restart my KDE/KDM without having to restart the whole machine.
The screen still wont resize on its own. Once KDE is up and running again you will need to go to the control center and change the resolution manually, but this time it should be listed. If it's not then you are using the wrong driver for your vid card and/or your H/V Sync settings are wrong. Check your card to verify your drivers, and check the back of your monitor for your H/V Sync (might look like this: "50-75 Hz" which means 50 V and 75 H).
Most cards will work using the "vesa" drivers. nVidia drives work on "nv" or if they wont work on that, use "vesa". Other cards I am unsure of because I use nothing but nVidia.
Hope I helped!