Hi ぽんたぽんた, Aub here. To answer your questions
1) We indeed has an algorithm that will cause the abilities that's related to your playstyle to appear more inside the dungeon. For example Str build will get more Str abilities.
2) 「残像」will give +1 activation time to「オーバーロード」abilities. So repeat x3 become repeat x4, not used up and activated again.