Close enough to get up to speed and off the launch rod, yes.Do you think you can light all three simultaneously?
One mix, poured or rammed with a scale, yes and yes.Do you think you can get fairly identical burn times? Do you think they even have the same starting mass?
Small --> considerable, yes.Lots of leverage turns a small force into considerable torque for a low moment of inertia object.
Miniscule --> very small.
The very small off axis forces combined with a sizable engine thrust will give a center of thust that is a miniacule distance off axis.
But we're beating a dead horse. Only a few launches would give the definitive answer. And that's if anyone were about to launch this (or a similay rocket) in such a configuration.