Ah thanks for the kind words, glad you like it! And to answer your questions, that's my bad for not making the text clearer, what I meant was: if the player would score points and the debt is not zero, decrease the debt by that amount and score these points instead.
So in your example with the Eyrie, say your debt is 3 and you're about to score your 4VP : the cardinals score 3, debt goes down to 0 and you score the remaining 1VP. Otherwise yeah it would probably be too OP with the interests on top of it ;)