24 GHz patch array with IE3D: Help needed

hello guys!

i designed a 24 GHz patch antenna array with IE3D and i would like to have some point of view on my design.i got some problems listed below.

1°) Why did i need to change the length an the width of the quater wave transformer lines to have the best match?
2°) what is the best configuration under IE3D to have the best results?
3°) at these frequencie, is my choice for ROGERS 5880 is the best way?
4°) what is the best method to feed my array
5°) when i put a distance about λg/2 between the patch element, i have sidelobes and the gain is not good.

if you have comments, i open.

thanks a lot.

a poor french guy :D