There is a huge difference between theory and hypothesis. Theory is a proven hypothesis, something can't be theory, unless it's proven. The question is which part of the Big Bang theory remains as hypothesis and which part is a theory??? The same goes for the black holes we have more than enough rock-solid evidences that black holes exist, but everything that happens inside the black hole is a pure hypothesis/speculation. 2nd law of thermodynamics, law of energy conservation for example have been and are proven over and over again, and that's why they are called theories. The very explosion of the Big Bang is still hypothesis, since we do not have enough concrete, rock-solid, irrefutable evidences, everything is pretty much indication or circumstancial evidence/evidences-basically this is the difference between hypothesis and theory. The only true facts are that everybody dies, and everything/everyone has the final end. Cheers.
There is also a huge difference between a tested theory and a proven theory. A theory is a tested hypothesis that has not been falsified. All theories are still subject to falsification and one of the strengths of science is tentativeness. http://arstechnica.com/science/news/2006/10/5609.ars http://en.wikipedia.org/wiki/Karl_Popper#Philosophy_of_science
