In my opinion, he shook his head less because he was outside. Trust me, the issue is something with his enclosure/environment. I had the same issue and already stated what fixed it for me. Something is bothering his sinus's, not his ear. I would take him off the medications also, there is nothing wrong with him that they will help with. Like I said, two of my previous rhinos were relocated and have never shown any signs of it again. Heck, my hatchling rhino's with start the head shake the next day if I just once give them unfiltered water from my well. Don't give it to them and they stop. It is something with the environment, trust me on this one.

Jacob