Probably not a popular opinion around here, but here goes anyway: the fundamental problem is that unless your net worth is $100m+, there is no point being a do-gooder as any attempts to fix big moral hazards are only going to harm you more than it's worth.
it's not about mending the world. it's about finding pleasure in living out what's right. it's embodying of a value, a moral principle.
the way you express it says that the breadth of the effect of your choices is an essential parameter in considering your processes. I dislike this position due to its administrative, almost corporate undertone; I do understand it and ascribe to it myself in administrative matters, but not the personal.
but look at it this way: you won't change much by feeding homeless animals or birds, or by planting a couple of trees, but it may still bring great pleasure to do it. one way that i see it differ from permacomputing is that the feedback / perception of its effect is more immediate; or that permacomputing is following a more abstract, mediated value. but both are about finding some joy and meaning in doing something purely out of care. if not pleasure, it at least gives a little framework, a heuristic when making decisions.
So why bother?