This is awful and so sad that you are still suffering.
IMO revenge does not necessarily equal closure, and the way the scenario plays out in your head is unlikely to be the reality. There is a strong likelihood that the OW is a master manipulator and you could be convincingly painted as the psychopath. You've had a taste of what she is capable of, so who knows what else could be unleashed. She may have already given her husband a convincing version of events to future proof herself against exposure. He may not even care. There are limitless scenarios, but what is 100% certain is that you have zero control over what happens next, once you have told her husband/thrown in the hand grenade. Even if it plays out as you would hope, schadenfreude has a short shelf life. I'm not saying you shouldn't tell him, but you do need to manage your expectations.
The fact that you remain so angry and hurt (not a criticism) is evidence that the OW and your husband still have power over your emotional wellbeing, so you could benefit from making that your focus. Maybe remind yourself that their thoughts, their lies, vile words and actions all came from a place of weakness, not strength. They fed off each other because they needed to, in order to feel powerful. Those are their weaknesses, not yours. Everything they said and did makes them needy, pathetic and vile.
Without necessarily realising it, you are the one with the power. You are the constant looming threat to the status quo. You are also stronger than you think. You are a mother, the breadwinner and you have spent all this time carrying on, sticking with someone who has caused you so much pain. You have put others before yourself. That all takes incredible strength.
One thing that prevents closure, can cause us to ruminate and spiral down, is the question, 'why?' If you have found yourself asking, 'why they were so cruel' or, 'why this happened to you' etc., I can guarantee your brain sought answers that threw up, and possibly continues to throw up, every insecurity you have ever had. Do NOT ask why, because the answers do not lie within you.
I suggest you focus your energy on making a plan to create the life you want. Treat this chapter as a valuable life lesson and use it to reaffirm your own wonderful qualities. When you cease feeling like a victim and feel 'indifferent' towards her and potentially him, you will know you are #winningatlife. I would make it less about closure and more about personal growth.
Good luck ❤️