Joe, your mind is not stopping you from attaining these answers, and I assure you that you’ve never gotten close. The answers to the questions you posed have no immediately forseeable answer; nobody can answer them just by “figuring it out,” such as what happens when you die.
And as Deman said, remember that we physically use all of our minds. Scans can show the electrical impulses moving throughout it; no doctor has ever said “Well, he was shot in the head, but luckily the bullet was lodged in the useless 90% of his brain.” If you want to talk about it on a sub-concious level… maybe. But who’s to say using “the rest”, if it in fact exists, just might make you better at math, or memory, or something? Sort of like
“You see that light in the sky?”
“Yeah.”
“Can you explain it?”
“No.”
“It must be a UFO!”
Time has proven that the absence of knowledge often makes us point to the paranormal. But more often than not, we find reasonable scientific explanations for these things, as time goes on. It must’ve seemed like common sense that there were dragons at the end of the world, or that only Gods could be the cause of a volcano eruption.
Just playing devil’s advocate here. I don’t really reject the possibility of any of these ideas.
Fear of the dark is also inspired by natural instinct; we are not nocturnal creatures, and thus at young ages we prefer light.
Walking on coals, I don’t know the exact art. I’m guessing you simply find a way to ignore the pain, like those monks who set themselves on fire. Yes, if you attune yourself correctly, you can disconnect your nerves, but I wouldn’t call that anything incredibly strange. I had an art teacher who could do something like that; you could smack him as hard as you could on the hand and nothing would happen. But the body is still taking damage.
On that topic, I find it pretty interesting what your mind can convince your body of. For example, some people only have to think of the sound of fingernails on a chalkboard, and they will get shivers up their spine. Imagination is teh powerful.