The salt is the least important part of the mixture. Until you get Kosher Salt, you might consider leaving out the salt. Bacteria doesn't like salt. That is why meat is treated with salt, to keep backteria away.
If it doesn't seem to be helping, then you have got to decide the value of the sinus floodings to your sinus condition. Now that you know how to do one, and feel comfortable doing a sinus flooding, then at least you have a tool that you can use any time you want, if you feel it will help you.
Sorry to hear that you are fighting cold like, or allergy symptoms. That is such a royal pain!
In my case, if the sore throat is in the top, or back of my throat, it usually is just my sinuses acting up. If it is the front or bottom of my throat then it could be a cold or infection.
When did your cold symptoms start? Have you done anything different, or eaten anything different in the past three days? If this is an allergy flairup, and not a cold, then one, two, three, four, five or more allergens have attacked you in the past few days, that weren't there before.
Just my humble opinion. Hope that you feel much better very soon!