I've found that dry air gives me a stuffed nose and sore throat, so try a warm humidifier, but not a warm/cold one. Cold running humidifiers can breed mold, and I find their mist tends to collect on the floor. Warm one's create proper vapor alongside the mist and absorbs into the air better.

As for dust, when I moved into my place and only had a bed I had no dust for the longest time and that's despite brick walls. So one way to get rid of dust is to have less stuff.

To keep dust down I have three Coway Airmega 400, a Dyson vacuum, a duster to knock dust off odd places, and I have a commercial mop and bucket. I've been considering adding a robo vacuum or mop to the collection. My understanding is they aren't much better than a dust buster, but that actually sounds pretty handy to keep the general dust level down between hand vacuuming and mopping.