There are damsels that are peaceful. You just need to do more research on them.Sorry... Damsels are mean when they get old and cranky. The are territorial and, soon, they decide the entire world is their territory!
Not yelling at you but this is harder than having a sump.I'm still experimenting with filtration. I'll get yelled at for this, but when my ta ks are getting ugly, I still have the best luck with a HOB (Yes, on a reef tank) and/or a canister aio alternative to a sump. The tank with a sump is just aggravating me, especially in the heat!
Purple algae(coraline or cyanobacteria) is completly different than dinoflagellates. Dino is brown not purple.I think the dinos are what you are calling the purple algae. Believe it or not, you don't want those parameters you listed before to be that close to zero. Too much nitrate, hair and bubble algae chokes out the tank (red and blue legged hermit crabs took care of hair, emerald crabs take care of bubble) too few nitrates and dinos choke out everything...
Keep in mind, this hobby really is fun!!!!