maxwell's equations (which I never learned, still interested) are expanded for magnetic charges at https://en.wikipedia.org/wiki/Magnetic_monopole#Maxwell's_equations . i've noticed sometimes wikipedia's citations can give more information than the article, if helpful.

it seems like those equations could possibly be used to plot a volume of magnetic charge as a function of field shape and strength.

regarding mass of a magnet, it seems like the force it experiences on it is going to be proportional to its field strength. so you might want magnets where field strength / mass is greatest, and at the greatest distance from the magnet. unsure.