Wretches have a 'Hit Rate + 95%' and a 'Evasion Rate + 5%' trait, I think those were the defaults, main character is the same. Not sure if this is relevant but the formula I'm using for skills is the same for all of them: a.atk * 4 - b.def * 2
I do have the invocation success rate pretty low (50%) on bare fist attack. I'll try bumping that up.
To reach the second ending:
***SPOILER WARNING***
You have to take the crystal back to the base in the graveyard and interact with a machine there to power it on. Then you can contact the SCP base, and so on ...