Well I competed the game in low chaos mode, I might stress that doesn't mean you don't have to kill anyone!
The first mission I ended on high chaos, then chose to try and limit the deaths after that, but I still killed. Some levels none other up to 7 people. So dont think you "have" to reload the level, unless you want that achievement/trophy.
I don't think you need patience in this at all to be honest, between blink and slow time you can happily waltz through a level, even with enemies seeing you.
As for Granny rags