Can there be chronic allergic sinusitis with only significant nasal congestion and malaise without any apparent mucus or nasal discharge?

Nasal congestion: Yes this is possible. You should see a doctor for an examination and proper treatment.

Yes: You are basically describing chronic sinusitis. Patients with chronic sinusitis typically don't have the nasal discharge that you get with allergies or acute sinusitis. But it can lead to chronic nasal stuffiness/congestion/malaise. Best study for diagnosis: coronal ct of sinuses without contrast - essential for diagnosis.

Yes: Chronic sinusitis can present in a multitude of ways including congestion and blockage in the absence of discharge. The clincher would be a decrease in your sense of smell and taste.

Generally not: Allergies usually cause a lot of mucus production, but typically aren't very important in people older than 70. Acid reflux that occurs during the night is a much more common cause of sinus inflammation at your age, and usually doesn't cause any nasal discharge. Work with your physician to make sure that your reflux (if present) is optimally controlled.