Actually it could be even better if he pays late this week, because he promised to pay interest up to the actual time he returns the funds. So paying late would mean that you will get interest for another, say, half a week. 
So just keep mum. Perhaps he will pay you after a couple of years. Then he will have to pay you more bitcoins than the number of bitcoins in existence.
But it is fully understandable, because pirate will not lower the rate, but continue to pay 7% for this week
