1. Set frame & titlebar to none. It removes the background graphics.
2. Persona window or stats bar or install another inventory window mod. Won't ever be on mine.
3. You can just resize that section to hide it. Most of the same information is available on the player window and the xp bar at the top anyway.
4. The color coding is identical to the big dotted number, which has a tooltip explaining what it is.
Have fun with the game and the UI.