Does two pellets hitting a point cause greater push than one pellet hitting the point?
Each pellet produces a fixed, independent linear force when it hits, along the vector it is travelling. Torque results for any hit will then vary based on distance from center of mass.
However, I suppose higher spread will technically cause some of those forces to cancel out when averaged over several pellets (since if they hit at an angle they will, to some extent, be pushing opposite to one another.) So heavy clip probably nets you a tiny bit of efficiency in this regard. Based on some quick math, I think you potentially "lose" up to 5% of each pellet's force at maximum range (you don't actually lose it, but that's how much is pushing sideways rather than directly away from you.) The amount lost however depends on the exact (random) variance applied to that pellet and the distance at which it hits; 5% is an absolute upper bound.
EDIT: Okay, I misread the question slightly. I think I answered what you *meant* (does two pellets hitting the same point produce more force than two pellets hitting different points?), but the answer to what you *wrote* is "Yes" because each pellet does apply its own force. The more pellets that hit, the more force applied in total.