re: Supernovae
"Then, theories must be revisited as to why so few supernovae are detected in our own galaxy."
Beautiful. This is something I love about science. You have pet theories that "everybody" starts accepting. Then better observations show that the theory as formulated does not fit observations. Bingo! Time for a major upgrade.
Think about it. If theory predicts multiple SNs per century, there has to be something wrong with that theory. Too many sigmas off the predicted rate. Flawed theory.