1) No, uniform density only guarantees that the probability of a particle being generated on a particular face is relative to the face's area. So if you have a mesh that is heavily subdivided and a mesh that is very low poly, they'll receive roughly the same distribution of particles. It does nothing to ensure particles are evenly spaced. You can use the separation setting in Position Object for that. Notice that in your screenshot you're scattering on a plane - the faces on a plane all have the same area so there will be no difference whether uniform is checked or not.
2) Thanks I'll look into it.
2) Thanks I'll look into it.