I would like the end of the pipe to form an approximate 270deg arc, as sketched, rather that the parabola as it is now:
I have no idea, which deform to use.
It is going to be dust-vacuuming pipe, the dust source a bit below the centre of the blue arc. As of the final shape, it is not precisely determined as far as it works well. In any case, the object should be bounded with two parallel planes from the top and from the bottom, as it is now, and the blue sketch lies on the bottom plane.