I just finished reading this which may answer your first question
I’ve been doing some testing with healing items recently, both food and potions. I believe the ‘drop’ in health you noticed when eating is not a drop at all, its your maximum health increasing; which makes your current health appear to be lower. It seems to be that when you are 100/100 on hunger, and perhaps water, you receive an increase to your maximum health and stamina of around 5%.
As for the enemies chasing you further I can only guess that they either may have increased leash distance or as you say they are closer for longer so stay engaged instead of leashing back.