Here’s how I think the situation with added shells of gas would work. In each image the brown represents the matter that has an effective attractive force on the red particle. The blue represents the area where the gravitational forces on the particle cancel out. What happens is that as the size of the shell of added matter gets larger the zone of attractive matter recedes. It looks to me that even if we extend the model to a 3d one that the mass of the zone of attraction would not overcome the weakening of the gravitational attraction with distance. In the limit, my guess is that the attraction would be zero.
	A particle placed at the periphery of a gas cloud. The brown represents the matter that has an effective gravitational effect on the particle
	As the shell of added gas increases, the effective zone of attraction (brown) recedes. The thickness of the attracive zone never exceeds the thickness ofthe original gas cloud, and in the limit of the shell of added gas being infinitely thick is infinitely far from the particle.