There’s basically no way to answer these questions using real physics I’m afraid.
It definitely can’t close it’s mouth faster than the speed of light. Yes it would have a strong gravitational pull, almost definitely so strong that it would just collapse into a black hole and not be able to exist. If it weren’t that dense, then it would basically just be a big diffuse gas cloud that couldn’t do much anyway, it would basically have to be a proto galaxy to not collapse into one.
If it’s using magic to exist, then anything is on the table.