I was kind of surprised to find out that Red was trapped in the mine for at least 30 years, according to his letter.
He sounded quite sane for someone in these circumstances.

Red's voice and accent are actually two of the most scariest and successful things in the game. there is no other voice that would suit better.
as for his death, i also don't believe he burned. how could he have guided the player through the game not knowing where exactly the player is? he somehow managed to give tips at precisely the right moments, like the player had a gps attached to his ass come to think of it, it fits well. the whole game is going from one place to another, picking up things and using them. it's like a big puzzle carefully prepared to be solved. maybe it's all just a test? maybe after completing the first episode we passed it?
things that also bother me are the little fragments of Red's posters. there is a big eye instead of a lady's face, and some other things. Red could have been watched all the time, maybe even guarded not to kill himself, but how could he then managed to make himself a loop to hang himself? he would have been stopped while doing that. instead he managed to make the loop and it would take a couple of seconds to hang himself, nobody could've stopped him. i think that his room was also carefully prepared to fool the player into thinking that Red was actually a prisoner. the voice in the incinerator might have been coming from a speaker, the key that he left was planted and the ashes were of coal or something else.
i also have another theory - either Red or Philip's father is the head of that 'experimenting society'.