Nose is usually the culprit in most ENT problems as is in your case. The germs causing the Sinusitis may be predominantly anaerobic which release sulphurous vapours causing the foul smell. The pus from the sinuses drain into the back of your nose and onto the throat. Here they come across the eustachian tube orifice which gets inflamed by this infected material and this causes the tube to become blocked causing the hissing or buzzing sound to be perceived called Tinnitus.
Next Steps
You need to aggressively treat your nose and paranasal sinuses. This will require you to undergo a CT scan of your paranasal sinuses which with guide us on the mode of treatment (surgical filled by medication or direct medication), that should give the resolution to your issue. Once the Sinusitis is resolved, the ears will automatically become fine.