Well, here's my somewhat-educated guess. What's important to remember is that Energy equals the mass times speed of light squared, E=mc^2. When something crosses the event horizon of a black hole, it cannot escape because it must goes faster than light to do so, which is impossible. Well, for a mass to become energy, it must go c^2 in speed. So really, mass that enters the black hole stays as mass but is crushed to the point of the singularity. The radiation we see from the black hole is not really from the black hole, but from the stuff around it. When things are close to the event horizon, they rub together with much friction, emitting x-rays that might be detected. But remeber that black holes are very small, and so detecting them is not easy. In fact, if the sun turned into a black hole (which it won't), things on Earth would be the same (without the light, of course!)So, as for the adding up of energy in the black hole, it is not totally plausible that everything that enters the hole will turn into energy: as far as I have learned it just adds to the extreme mass of the singularity. Of course, most of this is pure speculation because we cannot get any information from a black hole (well, there are theories on that too). As to other dimensions and universes, it isn't very likely. But who knows, maybe the Big Bang was really a black hole singularity exploding? interesting.....Tried to help, sorry if I misread your question or anything. :)