2. If the Big Bang started from an unbelievably powerful singularity,...after the explosion what did it expand into,...nothingness? And if we could stand at the edge of the Universe (if there is such a thing), what would we see,...nothingness. I mean does nothingness exist?
In relation to your second question, in the Big Bang model, the universe is finite, yet unbounded. In the related multiverse model, there are many universes, but they don’t overlap, and each may operate under different physical laws.
In answer to your second question, there’s no way to know until the light stops.