Why specifically do you suspect an ear infection?
Ear infections in birds are typically in relation to an upper respiratory infection, you should see slight facial swelling, maybe discharge from the ear and sinuses, and snicking, sneezing coughing.
If it’s a localized infection only affecting the ear you should see some discharge from the ear.
Lack of coordination can be caused from vitamin deficiencies, exposure to toxins or heavy metals, some sort of brain injury or stroke, or an issue with damage or something pressing on the lower spinal cord and nerves.
The most common cause by far is vitamin deficiency. Just because other birds aren’t affected that doesn’t mean a bird still doesn’t have it. Vitamin deficiencies can be caused by numerous things like parasites or infections or simply a less efficient metabolism.
You could put him on antibiotics, but without being sure of the cause that could deplete his gut microbiome needlessly. I would suggest putting him on a liquid multivitamin and a liquid B complex and see how that works out for a few days at least, you’ll need a 12ml syringe.
Squat over his back just enough that you’ve got him restrained but not sitting on him. With one hand pinch the corners of his mouth until he starts to open, open his mouth and insert the syringe as far down the right side of HIS throat as you can, then hit the plunger. Hold his beak upwards for a moment so he doesn’t spit it out.
If he tries to throw it up let him, it’s better than letting him aspirate.