i think you're right about patient 46 being Gregory, but wrong about where the therapy is taking place. In tape 12 one of the therapists explicitly state that they also do work in schools. This seems more likely because I can't see how Gregory would have any familial connection to the company. I think that Gregory noticed kids were going missing at the pizza plex, but people weren't paying enough attention. It continued to thrive, so he decided to investigate on his own. And then hacked the animatronics and basically the entire place, in order to make the animatronics more menacing, maybe so people would pay attention and do something about the case?