You poor thing. You've been through the mill trying to find out what is wrong with your boy.
Lady has Grand Mal seizures that seem to last forever, but they really don't and she comes out of them by herself.
I guess trying to check his blood glucose randomly throughout the day is the best idea. Then you would know for sure if he is hypoglycemic. I don't think I'd put too much stock in a BG test right before a seizure since the blood glucose normally drops then.
Lady gets both phenobarbital and potassium bromide. Phenobarbital is hard on the liver, but you can give supplements to protect it. I have given Lady milk thistle almost right from the start and now, after 9&1/2 years, her ALT is finally elevated. I adopted her at age four and she was having seizures every few days so who knows how long she'd been epileptic. Pheno alone didn't control her seizures. They were better, only every few months or so, but after about 1.5 years she began having cluster seizures. We added potassium bromide then. That controlled her seizures and she hasn't had one in two years now.
Keppra is also an anti-seizure medication that I have heard great things about.
I pray you can find out what is causing his seizures and get them under control. Seizures are horrible to watch. You never get used to them. I can't imagine how much scarier it would be to have a dog that couldn't come out of them by himself. You must be terrified to leave him.