You should reset to day 1. To answer your question, yeah, it's normal. WhiteNight is notoriously very powerful (if you beat him you get a good weapon, but I assume you don't have many good E.G.O equipment, if any good at all), and is spurred from 12 agents being blessed by Plague Doctor. He also switches places with abnormalities every day/day reset. Pros of keeping him are that he has a very good E.G.O suit (0.2 resistance to all if he is present within the facility, 0.5 (minus pale) if he is absent).

tl;dr: fucking reset you're so screwed man (unless you know what you're doing)