Ad 16 adjusting the black area of pcb is not done with Keep Layout, it is all water experience. The correct way is to click on the pcb, press the number key 1 and then press D. You can see that there is an option to move the vertex of the board, click (shortcut key V), and then you can drag the fixed point yourself. After setting the size, press 2 to exit, and the black area will change.