Have you tried IsoCort or any direct Cortisol replacement??
I really think you have it figured out, and others are now mentioning it. Your Hypoglycemia must best related to your low Cortisol.
Also, you said that the Vitamin B you were taking was helping the Hypoglycemia temporarily. Why not take Vitamin B3 (in the form Niacinamide) at night before bed. A small dose (started at 25mg - worked up to 120mg) has made a big difference for me at night. It took about 2 weeks before I felt it, but I started nothing else during that month and it has remained consistent for more then a few months.
If it doesn't bother you, give it a shot. It's also dirt cheap. But seriously look into that Cortisol replacement, if you haven't already.