I have sleep apnea and use a CPAP machine nightly. My CPAP device comes with a humidifier chamber to keep the humidity of the air I breathe in high.

One of the side-effects of using a CPAP machine is that sinus congestion never bothers me as long as I have the device on. It provides enough pressure that my sinus are forced to remain open when turned.

So maybe look into using a CPAP machine to help you out.