I'm having the same problem. Have you figured it out yet?
Very late answer, but if you're still interested in that:
You need to gather all 12 clues, and then the option to take them to the interrogation room will appear when you talk to them. It's there that you'll make use of all the clues acquired.
Also totally agree on the MC's disposition to mean behaviour. Most of it is optional (like, you don't really have to blackmail the nuns, for instance), but there's a lot of content that is gated behind being a bordeline rapist, unfortunately.
But I just love everything else way too much to drop it, haha.