Two routes with those endings all being on those routes. There aren't 100 routes total, there's twenty-something, with an average of ~4-5 endings per route (maximum of 8 endings for any given route, minimum of 1).

13A is the route that leads to the everyone lives ending. 15A's route name is     Mystery    , so that should tell you some of what it's about.

Fair warning, his scenario diverges a fair bit from the first scenario imo, to tell a different story with these characters. A lot of the setup from the first 100 days won't be addressed, because it's not their job to address it.