Older guy here, been divorced, and seen many cases. Some things to remember as you go thru this:
1. Apathy is the opposite of love. Not hate. Anger against the other man will do no good, and if not him, it would be someone else. Hate and anger mean you are still involved.
2. Move any cash assets out of reach someplace safe immediately. You will need these assets.
3. Get competent legal help and file the divorce paperwork immediately....immediately. The details can wait. What this does in most states is set the date for legal separation, after which she is responsible for her own bills. Contact the credit card companies as well. You don't want to have to pay for her fun with the new Beau. She will know in a few days of you filing...she will be served. Plan a discreet move out of items you value if you are moving, do it when she's not around.
4. Never show anger. Never send anything angry via phone, email, etc. Assume you will be recorded. You may. Speak to her in vague, non committal terms. Maybe, ya, I guess, dunno, could be, let me see about that, ..etc. anything firm follow up in email. Anything anger related will be used against you.
5. Understand you are a litigant subject to the court. Nothing more, nothing less. Manly ideas of physical fighting, confrontation, etc. are not beneficial in this forum, rather detrimental. ALWAYS remember you are in business litigation. Your goals are to minimize costs and maximize your degrees of freedom.
6. She may play with you. Maybe at the time believing it, maybe just to manipulate, but she may ask to come back. COMPLETE the divorce. I've seen many men take them back, stop their legal protections, only to see it get worse later. If she trys this ploy, tell her maybe, let's see, I am thinking it over, give me time, try to use it to settle amicably. Stall and delay until final filing.
7. Close circle of friends, family, and the wife of the lover deserve to know and will find out. They all deserve and need to know who they are dealing with. Beyond that vengeance is unnecessary. Apathy and living well is the best vengeance. She's already shown she doesn't give a sh*t. She's just going to think you're an a hole that deserved it, look how you treat her now! Friends and family will empathize, you don't need that.
8. Assume any communication with the opposition is for a purpose. It is. Treat it as such.
Best of luck. Keep busy, don't waver. It only gets better when it's done. There's life after divorce, adultery, etc. Keep busy.
Prime_Beef