Is it safe to fast 8 hours before sleep and 8 hours while asleep to reset circadian rhythm? i'm seemingly healthy, but can blood sugar go too low etc?

Difficult,: but probably safe. Unless you have a diagnosed blood sugar defect such as diabetes or hypoglycemia your blood sugar regulation can manage regular prolonged fasts. There is, in fact, quite a bit of convincing data that calorie restriction and intermittent fasting can have notable health benefits including longevity. Keep drinking water. Cravings and grumblings ease after a week or two. Best wishes!