ambivalent on how to trade off between their selfish and philanthropic desires

Imagine I offered a real match, pulling from some pool of money that wasn't yet allocated for giving or self-spending. The leftover money would go into my self-spending pool. Then I need to not adjust future years self/giving division based on this extra self money.

This only works because I have carefully divided self-spending and giving pools of money. Otherwise while you and I both might think I was providing a real match, in reality the money might have been going to end up being donated anyway a little later.