First off, well done, sounds like your getting your numbers down. Keep at it as it sounds like what you're doing is working well. Secondly, you will never achieve exact precision with your number on a day-to-day basis even if you've done identical activities and meals. This is because a large number of factors go into your sugar levels (exercise, food, weather, stress, insulin absorption variability) and your meter is only accurate to within 10% of the actual reading.
That being said, you should aim for figures that are fairly consistent on a day-to-day basis for equivalent readings. The best way to do that is to get into a daily routine including exercise and eating (and injecting) at similar times.
To answer the drop in sugar levels at midnight, can you tell us what insulin your are on, what time you injected, what you ate that evening and if you did any exercise.