@oceanayers I am wondering if his sympoms will start improving with clear sinuses . new research is out about how bad mouth breathing is for you including some of the symptoms you are talking about. Poor sleep, which has its own complications as well as lower oxygen levels.
nasal breathing promotes nitro oxide which relaxes the blood vessels for better oxygen levels in the lungs.

Respiratory & Systemic Health
Reduced Oxygen: Bypasses nasal nitric oxide, which helps lungs absorb oxygen, leading to lower oxygen levels and fatigue.
Poor Sleep: Linked to snoring and sleep apnea, disrupting restorative sleep and causing daytime tiredness and irritability.
Infection Risk: Bypasses nasal filters, allowing unfiltered, cold, or dry air directly into the lungs, potentially increasing sinus and ear infections, says this dental website.
positive thoughts to him