I'm so sorry, I feel for you. I have sinusitis that I have been battling for over 20 years. I take Sudafed. The real stuff not the PE stuff. This will help break up the yuck inside so that it can't get infected as easily. I am not a huge fan of the Neti pot either, but, it helps and it works. I also have the giant squirt bottle from the same maker and it isn't as bad.
I did take Claritin one summer everyday and I didn't hardly even need the Sudafed, nor did I get any sinus infections. In reality, I get an infection and need antibiotics about 3 times a year. Fall, Spring, and Summer.
Make sure you stay very hydrated because the mucus needs to have enough fluid to flow out.I remember when we were little we used a kettle on the woodstove to keep moisture in the air, but you said you have misters going, so that probably isn't the problem. Air quality in winter tends to go down because of being closed up. One good idea is to air out the house every so often even if it is really cold, snowy, raining, etc. outside. This really really helps!
Good luck, I feel for you so much!!! Oh if you can't get the Sudafed from the pharmacy since it is behind the counter but over the counter in most places, then get a prescription from your doc. Here we have to have the prescription, but if we drive across the river to WA we can just show our ID and buy it from the pharmacy.