I have noticed myself about aggression being directly linked to the light being on. Therefore, if I saw my fish harassing one another I'd just turn off all the lights and if it was during the day- throw a blanket over the tank.
As for swords, I'm raising a whack load of them currently. They all get a long fine. But as soon as I introduced them to a new tank: BAM! They all start pecking at one another! Pretty much it's to establish a fish hierachy. They should stop within a week, but sometimes, if a fish starts doing badly, it means there was something wrong before and that fish could tell. Survival of the fittest, they'll pick on the weaker. So you may want to look into that.
Yes you can keep the female on her own, but they don't do so well. Two females is a lot better. And the ratio with males is 1 to 4 or 5. I currently have 1:5, but that's just how they ended up being sexed. So cute when they sprout their swords!!!!