1/2. It makes sense to ask the question, though as others have said, the naive answer comes out correct. Money is fungible, that's the whole point of money, so if you assume the organization's internal operations are efficient then your intuitive answer will always be the right one (if "your" $5 was spent on repairing the employee coffee machine, then that will be because the organization believed that repairing the coffee machine would improve their working efficiency enough to do $5 worth of extra net-distribution).

3|. Open question. Many on this site would say it's worthwhile; my instinct is it isn't. We can't judge moral questions by anything other than our own moral instincts (see The Moral Void). It smells Pascal's-mugging-ey to me.