Has he gone to an Ear Nose and Throat doctor? I ask because there could be different things going on contributing to this. Ear infections or viruses can cause this heavy ear as I call it (when it feels full and sound is muffled) and ringing. Is he dizzy as well? The infection or virus itself can cause it. But if you have an ear infection, it also can cause a bit of damage after the fact as well. Another common issue is Eustachian Tube dysfunction. This tube can crush in on itself and cause ringing and fullness/hearing disruption. An ENT can work on that with you. Reverse ear pops is on way to combat it, often otc antihistamines are recommended and a short course of pseudophedrine. I'm assuming that they got in there and cleaned his ear as well to make sure simple wax wasn't contributing to it (it can). But I'd consult with an ENT for next steps.
I'd want to know if there is any actual infection in the ear. If a swab and culture shows negative, then everything is likely inflammatory.