Why does the true ending require you to abandon your friends on a second playthrough? Because you actually aren't doing that; you're just simulating the idea that Eriko went back to Illbleed by herself as presented in the first ending. Not rescuing them during the second run means that Eriko is well and truly alone.
Dummyman always knows where to find you because he personally operates his branded photo services. As a result, he likely has access to the photos you take for quality purposes. It just so happens he uses what's in those photos to get the jump on you on the side, privacy policy be damned.
Why is Eriko still susceptible to dying of shock even though she has no sense of fear? Because being startled is an involuntary and instinctive response of the human body. She isn't afraid of the stuff that pops out at her, but it can still catch her off guard and her body will automatically increase her heart rate. And if her heart rate is already too high thanks to said response, well, being fearless doesn't stop heart attacks.
It's mentioned that 100 guests die each day in the park and we're left to wonder why nobody goes to jail. Except that a dead PC can be brought back for $75,000. This is a setting where death is as treatable as a broken leg, although the doctor's bill is a tad pricey. It's also likely that you're actually killing staff in combat, and part of their staff benefits involve paying for a ressurrection. Death has been conquered; mastered; made into a game for... well, not children, maybe wealthy adults.
