The abyss has no "bottom". It's called the "bottomless pit".
The Abyss does have a bottom otherwise the world would turn inside out
Not necessarily - otherwise the same would apply to a black hole. A black hole is a vacuum within a depleted star which has no "end" either - or in other words "bottomless".
Scientists estimate that the Laurentian Abyss is about 6,000 meters at the most in depth. The Laurentian Abyss was used in the Transformers: Revenge Of The Fallen movie.