I don't have any experience with EC, but I wanted to say that it makes sense that he'd have those symptoms with it. It seems like he has vertigo, which is a problem with the inner ear, which has sense organs that tell us which way is up and if we're moving. Vertigo is a problem with them--the sense organs are telling the brain that he's moving when he isn't, and that up is down, and all of that. That's why his eyes are moving and he does those crazy moving about things--he's trying to figure out which way is up. These sense organs have a lot of neurons to tell them what's going on, and since EC can have an effect on the nervous system, it would make sense that vertigo would be a symptom. Now this is based on what I know of neurobiology, not of animal health, so it may not be valid in this case, but it makes sense to me. Humans with neurological issues can get vertigo too.
Hugs to you both, you and Pippi are very brave. **sending healing wishes**