Goyya
I wonder if any of this will effect Kisuke's soul. He's having his soul damaged/repaired multiple times- So it may cause his soul to get stronger; provided said injuries are healing properly. Also will the discarded parts effect him? They are bringing their own bodies down to their souls level- meaning that said discarded parts could be potent. Kisuke is far stronger so perhaps he can integrate these parts into himself. Heck hey may eventually need to... So he can face of against the backlash.
In the author comments, it was noted that Serafall likely would have PTSD or similar trauma based on her past experiences, which I would agree with if she were human. To much is unknown about devil psychology (given they are a fictional species), but they are likely very different from human psychology.