Except that the ball does momentarily stop, and the floor does budge. Every time you move, the Earth moves in the opposite direction.
Not quite. You can't always say "move" when talking about reaction forces because sometimes there is no actual displacement. The Force is still applied, but because it's an opposite and equal Force the Earth doesn't actually bump itself up to make the ball bounce. That would be an unequal Force.
For a change of direction to occur the moving object has to not move for a very short amount of time.
Actually now that I think of it there should be a perfect conservation of momentum in that change of direction too. The unstoppable force will lose no energy to the unmovable object, since it shouldn't absorb any energy.