@Wayne18000 . It's a difficult one to answer. We are all different, affected differently by going hypo, different hypo treatments for different people.
As for how low can BS drop? There are people who have been as low as sub 2. What is probably more relevant is the speed and circumstances of BS dropping.
If your sugars are dropping rapidly you may well go into a serious hypo at 4.
If you're dropping at a slow rate it's possible to go sub 3 and still be able to self treat.
As for hypo treatment, that again is a personal choice. For me a rapid drop in blood sugars would see me drink glucose powder in water and orange cordial, followed by complex carbs if possible. A steady drop in sugars would be treated with a few jelly babies and then some carbs.
This all applies to me being T1 diabetic.
Not sure of your diabetes status, if at all.