I'm looking at your first Photograph with the Ruler. Look at the "er" of the word Porter. Now look exactly at the Right hand side of the ruler with the numbers. Right above the "er" I see the measurement that says "3 3/4".
Hexagon Blocks are measured according to the length of each side. Take some cheap fabric like muslin. Cut one strip, then use your 60 degree ruler, and go ahead and cut three or four triangles. Or cut six to make a full Hexagon block. Sew them together. Measure your sewn sides, the six sides of your perimeter. Are you happy with your muslin block?