So, it gets fatter and fatter as more mass accumulates until the event horizon becomes full, and if more mass comes in it pops like a soap bubble?...................
Nope. More mass just makes it keep getting larger. It is pretty interesting (coincidence?) that the Schwarzschild radius of a black hole with the mass of the observable universe is pretty close to the actual radius of the observable universe. That is a black hole with the same mass as everything we can observe would be approximately the same size as what we observe, leading to the question- Do we actually live inside a black hole? This possibility is studied seriously by some theoretical physicists and can actually explain the expansion of the universe from a minimum size.
It’s hard to see, however, how this possibility could ever be confirmed (or refuted) observationally.