I used the default vaule given in "ff_radiation_plot" analysis group. N theta and N phi are both set as 25. Should I increase it more? 

 You made this comment earlier "A plane monitor can only collect power forward (transmission) or backward (reflection). the total power is the transmission amount.", only forward and backward monitors will not give the total power. As it is a dipole, it will radiate other directions also. And the placement if forward and backward monitor will be related to some collection angle and to collect the maximum information (High numerical aperture (NA)), I need to place a monitor in the near field.

But the better option would be If I am able to integrate the whole 3D far filed profile and the upper part of the profile. The ratio of it would be the collection amount in forward direction. The ration would be independent of the collection angle. Can you please suggest how to do this integration?