1: MWhen you have made a selection (colored segment) just place your curser outside the selection and click. Selection will go away. Does not matter that the little yellow triangles stay where they are. They will automatically go to any new selection that you make.
2: Many ways. One: Click on ignore event grouping icon in toolbar. All grouping will temporarily go away until you unclick it. Two: Highlight (click on) either the video or audio (not both) and hit U (Ungroup) you can then move it independantly.
3:Its easier to move smaller distances (ie 1 frame) by zooming in on the time line then use arrow keys.