Found my solution through trial and error. It helped me to imagine that the horisontal spacing left not used by the width of column 1 and column 2 should be split equal into 3 (space before first column, space between both columns and space after second column).
For reference this is what I did for the X Position.
Column 1 position:
(1920-(c1w+c2w))/3
Column 2 position:
(1920-(c1w+c2w))/3*2 +c1w