Well, Gravity is the attraction between particles. On the macro, newtonian scale, this would mean the attraction between two objects. (As objects have connected particle fields which act as a single unit)
Increase G would indeed increase the forces of attraction between the two relays. But remember that as the radius (distance) increase, gravity gets less potent at an increasing rate. So even a much higher G would have negligible effect because the r is so large.
Now, having a high G would also cause the ship to be more attracted to each relay. But, as above, because of the Rs, it would be exponentially more attracted to the relay at which it starts then to the destination relay, so it wouldnt move.
