as far as how you crop with ffmpeg, its like this...
ffmpeg -i in.mp4 -filter:v "crop=w:h:x:y" out.mp4
where w, h, are the width and height of the output video, and x, y are the upper left corner offset.
If your original image is 2520 wide and on your screen, thats 10 inches wide, measure to where you want that left edge, say thats 3" from the edge of that 10" wide screen... so 2520 * 3/10 == 756, thats your X ... your W could be 2520-X == 1764 would be the width, unless you want to crop from the right. If you don't need to crop off top or bottom, then Y = 0, and H = whatever height the original is.
ffmpeg -i in.mp4 -filter:v "crop=1764:1520:756:0" out.mp4