I was a military wife for over 20 years so I saw the Uniform Code of Military Justice through my H's eyes and I can tell you it is there for a reason. Military guys (and gals) have to be able to trust the judgement of their superiors without a moments hesitation. Do you think in a time of crisis that anyone who knows about his affair would trust his judgement? Would you follow one of his orders without hestiation or would you try to second guess him?
Reporting him may feel like revenge to you, but in the long run it just may save the life of one of your men. If I was in your shoes I would not hestitate even a moment in reporting his actions.
