1) It's a known problem. On my camera, it's around 1 small flick per second. If I block the events which make Canon FW draw over the menus, the camera becomes unstable. Patch welcome.
2) Put your hand near the LCD sensor to clear the screen. In LV it clears itself.
3) Only works in manual (photo and movie) and P, Tv, Av.
4) Never happened to me (and I go back and forth a lot of times). Find a sequence of key presses which locks the camera and report the problem.