I can totally appreciate how you're husband feels as far as wanting to know every detail because I am presently going through the same thing with my wife, except she has no longing to want to leave me. I would advise you answer his questions completely honestly, as much as it is embarrassing for you and as much as it will be painful for him, you owe him that much!. You must not bend the truth or soften the blow in any way, this guy needs closure as the not knowing is always alot worse than the lies. Good luck.
My Story: Repost: My Story, Wife Cheated