My ex-best-friend's fiance was from Holland. She told me the questions were very personal. They ranged from favorite TV show types, to frequency of sex. The INS is trying to make sure you are not marrying to get someone a greencard. You must prove the marriage is legit and that you are not marrying with the intent to divorce after a specified amount of time just to gain someone status. Carrie and Martin were marrying for him to be legal as a favor to her real fiance, Sean. Sean and Martin were best friends for years and martin wanted to move here. So Carrie and Sean decided she would marry, then divorce, Martin. The questions were so drastically different that the INS declined Martin a card because the noticed the patterns of simple things being different. Of course! They were just marrying for the citizenship. My fiance and I can tell you the other's favorite coffee cream, TV show, shoe size, etc., and Carrie and Martin had different answers to: Did Martin like meat? She said yes, but he's a vegetarian. A couple who know each other would know that.
So sorry, you'll have to bear the questions, however personal they may be.