I started to write a response to this and then deleted it because it grew to over a page and I wasn't close to being finished. Basically you are looking at things from a utilitarian point of view and would like a description of my position in terms of a utility function. But I don't accept that point of view, even if I understand it, and the most natural description of my way of acting isn't a utility function at all.

(I accept that to the degree that my actions are consistent, it is mathematically possible to describe those actions with a utility function -- but there is no necessary reason why that utility function would look very sensible, given that the agent is not actually using a utility function, but some other method, to make its choices.)

The simple answer (the full answer isn't simple) to your questions is that I should do the right thing in my life, which might involve giving money to strangers, but which probably does not involve giving 50% of it to strangers, and those few people who are in positions of power should do the right thing in their lives, which definitely does not normally involving wiping out countries.