First, you can't directly "landed damage" message to perk points (or score, too).
Second, the perks gained by bombing are computed in a similar way as the perks for shooting down enemy planes, it's just that instead of your plane's ENY value the OBJ value is used - which means there can be differences between different arenas, as planes can have different ENY ratings in different arenas. And of course that also means the perk modifier applies, too. You get much more perks when flying on the outnumbered side.
And the most effective perk farm bomber is the Ki-67.