It sounds as if you have a glucometer since you said you have checked his glucose levels. Do you know what is considered "normal" in glucose readings? Glucose levels for non-diabetics and for diabetic people go up and down all day long. Most doctors don't consider glucose levels to be too low unless they drop below 70, but a person can start to feel a little bit bad if in the low 70's, so this might explain why your son didn't feel like eating when his sugar was at 73. Sometimes we can feel a little bit nauseated and can completely lose our appetites when glucose is a little low. It sounds as if you are doing the right thing: if he is a little bit low, give him a little bit of juice (it doesn't take very much -- say about a half cup or maybe 3/4 cup) and then give him about a half hour to digest the juice and feel better before trying to get him to eat or do anything. It may take that long for his glucose levels to rise to normal and for him to feel OK. Do get him to a doctor to see if you can find out why he is having the seizures. Very low glucose can cause seizures, but the levels must be much lower than in the 70's for this to happen. So all possible causes should be checked out.
You are dealing with an awful lot here-- it must be exhausting. I hope you can take care of yourself through all this.
I am just the mom of a teen diabetic, not a doctor, so I can't give medical advice, and your situation sounds complex. I will say that the blood sugar levels don't suggest diabetes, but the drinking and urination suggest that something is going on. 73 isn't dangerously low, but I don't know much about hypglycemia.... it's worth testing for that.
Perhaps you can do your homework now to find a good endocrinologist, and make the appointment (because first visits can often take many weeks to schedule) for the minute your new insurance kicks in. You might also need to see a neurologist because of the seizures-- they could have a source that has nothing to do with endocrinology.
Has anyone else out there had any experience that relates to this?