Violet, this is one of the hardest balancing acts that I can think of.
If I need a fast increase in blood sugar I use juice or glucose tabs. Since I have a lot of trial-and-error data, I know that 4 grams of glucose or very simple sugar raises my bs 20 points in 15-30 minutes.
If I need a nice, slow absorption and I want it to last a long time, then I use starch, fat and protein snacks. Starches absorb slowly, fat and protein delays absorption so it makes for a nice slow burn. However, 4 grams still raises me 20 pts even though I might not see it for hours.
It doesn't matter that you already had your snack if you find yourself hypo, unless the carbs you ate are not absorbed yet and your bs is rising - but if you are below 70 and dropping it's better to treat like a hypo than to gamble your bs will rise in time.
AM blood sugars are very hard to control. in the morning people tend to be a bit more insulin resistant. Plus, many of us have a liver release of sugar in the AM, causing a drastic blood sugar rise - even without eating. There is even a liver release due to a mild overnight hypo (3AM is the witching hour) so sometimes eating a little more at night result in a lower AM blood sugar. A lot of us test at 3 if we think we're into some weird area like this. You can look both of these up on the internet, the phenomena are called Dawn Phenomenon and Somogyi Effect.