cramped pies

This is a story about physics, a slightly hostile alien race, and a really big black hole. But really its not a story at all but a bunch of questions. Questions I'm hoping someone cleverer and more learned than I can answer. If you think you have the answers please post them below. The story starts with an alien race, a type 3 on the Kardashev scale. This particular alien race happens to have a presence in our galaxy and the story starts as they become aware of our existence. Their astronomers detect our planet and our existence on it, probably by the effect we have had on our atmosphere, but maybe also by our radio emissions. Once detected they go into full scale investigation and determine we will eventually become a threat to them if left unchecked. Reports are written by their scientists and handed up to their governing structure. Estimates of how long before we start to expand outward into other star systems and how long before we, or our AI, start to turn the entire gal...