Perhaps others can give reccs on resources or prep items, as I am no expert in this area. Our son was fortunate to have been offered a Type 1 award after the first board. We are not a military family so we had no background in this area. That said what I can offer is what I told him..." Don't over think an interview , the person you are and your own nature are what got you the interview in the first place. You have been successful to this point in life being exactly who you are, so why be anything different? Go in there be the respectful, humble but confident person who you are and speak from your heart. " Obviously that worked out for him. Not to over simplify things but I think if any kid can be confident in his own self he has any interview licked.
What I can say is the officer who interviewed him essentially spent 50% of the hour just talking to my son and doing all the speaking, explaining the AirForce, ROTC etc..the last 30 mins was question which actually seemed to be read directly off a script. (I know this because I was able to hear it sitting in the lobby) . I don't feel the actual answers provided really mattered as much as the style and the confidence with which you answered. Look people in the eye, don't fidgit in your seat, feel comfortable in your clothes etc..I'm sure your son will do fine! In a nutshell I would say don't add more things to his plate in the next 2 weeks rather spend it building and validating his confidence . Best of luck.