Is it at all possible for you to either take a break from work, or work part-time, just for a while so you can be at home with him? I realise it might make things difficult financially but it wouldn't be forever ... .
I was wondering about a partial or focal seizure of some kind too but I see you have already considered that. My Sophie had some recent episodes of strange behaviour (fly-catching) which the vet said were considered to be a form of mild seizure. I did a lot of reading on the internet at the time about partial or focal seizures and it seems that during these "seizures" the dog sees or smells things which aren't there. Altered vision is also mentioned as a symptom on some of the sites I looked at. FWIW, we gave Sophie 10mg Valium when she had these episodes which calmed her right down.
Hope you get to the bottom of it.