Not sure why you got a downvote.

I would be quite interested in understanding how to quantify or otherwise make suffering visible.

We try quite a bit on heuristics to try to avoid suffering but in the end we cannot avoid it. Thus, with animals we are quick to euthanize them when they suffer a lot (again for which scale) but for humans we do not.

I would like to understand if there is something like that.

To the topic of longterminism: cool idea to think about it but completed useless in every day. It is mental gymnastics. Like sudoku. In the end nothing practical comes out of it but you had fun thinking about it.

From a more pessimistic perspective: this is the sociological equivalent of terminal value calculations in Discounted Cashflow (DCF) calculations. It is the sum of all future possibilities, weighted by probability and discounted for time value and risk.. needless to say, it is a perversion of the value of life to apply this to future human beings

Edit: and also quite utilitarian, void of any ethics as the focus is on human beings alive and to be born, not what they do with their lives.