Regarding the blades of grass issue: we cannot understand the number of neshamos Hashem makes. We cannot truly understand the concept of infinity either.
Why does a blade of grass not get an “equal” neshama?
We will never know the answer to this in olam hazeh and to try to understand this is foolish. But to compare blades of grass and people to tailors and talmidei chachamim is also foolish.
Unlike blades of grass, people are capable of feeling pain in olam haba by the “chupa of ones fellow”. This pain cannot result in olam haba unless it is derived from “equality and fairness”.