Forgot to mention on the background. You will need to recalculate the normals to inside.(Shift+Ctrl+N or alt+n->Recalculate inside). Also create a second background light. Select background light. Press Alt+D and left click. Open N-panel and in the item tab->Transform panel->Under rotation click in Z and press End key to move to the end of the number.(Note it ends with a D) then type *-2 and press enter. This will double the the number and make it positive. Move mouse cursor over X under Location and press the minus(-) key. Do the the same for Y location. This should give you the same lighting on both sides.
