You stand a chance of being left with half of everything if you hire a clever attorney. If you decide not to split (and you adore the lout, obviously), consult an attorney anyway. Not very Zen, I know, but a lawyer will help you figure out what you want, concentrate your thoughts, and give you confidence, knowing you have someone in your corner.
Then, over cocktails, or sometime when you’re not rushed, tell your husband you saw his bank statements and that you know he’s having an affair. Don’t be treacly. Don’t cry. Don’t squish Kleenex into your face, and be prepared for him to attack you for snooping. Hold your ground.
Then wait for him to calm down (and shed about six ounces of persp). If you stay strong, drop the helpless-wife act, and tell him exactly what you want…I think you’ll have begun the first step of a journey that could lead to a v.v.v. unboring marriage. Or divorce.