Maybe it would be "easy" if he listened to the advice he received when he first started a discussion on this topic. If you have the attitude "I don't want this, I won't try this" how will you solve the problem that brings you the 10 BTC reward? If I were in his place, I would try every advice and try all the possible dates that came to my mind - because if the password is really a date set by his father, then he didn't make up some nonsense date, but it is something that was very important to him.