The values for the x-axis and y-axis are going to significantly depend on what you exported and the orientation of the observation line. Based on the naming (and content) of your f2d files it appars you exported the Hy field component for both observation lines. Additionally this your observation lines appear to be x-directed (normal of the line is the x-axis) so the line is along the z. Therefore the following items are true:
1. What you exported was the Hy component of the field
2. Based on the content it would appear that you have exported the amplitude (A/m), phase (radians), and intensity (A^2/m^2). If you compare it to your results in the FDA file you will see that this is true and therefore these quantities are you y-axis.
3. If you refer to the user reference under the help documents you will see the data format for the f2d files. For your file (opened in notepad) the first few lines are shown below. The first line is a file identifier, second line is the number of data point, then each line is a data point with being printed in “x y” format. This can be directly copied and pasted into excel, or you can rename the file to .csv and open it using Excel’s text file import funcationality.