no it isnt. 500K, no Deaths = 500K/1L = 500K/L. then you get killed and you get another life so now its 500K/2L = 250K/L.
no it isnt, thats a lifetime. eg. you havent died yet, but you've still had a life ...
Life span is what matters. A life is an undefined time period, and as such can't be used in the denominator of a fractional ratio because it is continuously variable, ruining the point of the ratio which is to define the number of things you do per a a unit of something else.
Before your first death, you have not completed a full unit, and how far along the unit you are is indeterminable. It is defined at death. The death is what makes the units consistant. Without the death there is no fractional ratio.
So it should be life spans. And again Tilt is correct.