1. agree with 2 pairs max in 30 gals, as said above
2. No, adding more females woul not improve the situation.
after pairs are formed, the extra females will get chased by the 'official wives' and they will get stressed to the point where they might die.
at the same time, the wives will still quarrel as expected, so no advantage whatsoever.
males will quarrel with each other, they rarely have a go at females, perhaps when spawning, but otherwise their main business is with males.