But teleportation, alternate worlds, immortality, etc are all old ideas. Thousands of years old. Transcendental mediation, just for one example, is pretty accessible.

There isn't answers for everything, and if you keep asking "Why?" you eventually will hit a wall; that's how it is, even in Mathematics, which forces you to define axioms before trying to do anything.

"we don't know, we just have theories" is some false humbleness, though. We do know a bunch of stuff, we know for example that exceeding the speed of light breaks causality. Can it be done? Well, it could, it would just break causality.

> "I was a believer from the first chapter." I haven't read the said book, but it looks like to me that you just want to believe, as you said yourself, something different.

Go look on Wikipedia what Solipsism is, seems you're headed that way already.