Separate bank accounts, get your work pay check deposited into another account deposited into another account or you will find yourself with no money and a lot of reasons from her as to why she should spend as much as she wants. You do NOT owe her anything. She cheated on you and wants out of the marriage, remember? Why would you owe anything to someone who did that to you? Because they're your spouse and because you have kids? What about you? What does she owe you? Nothing after all these years? Stop being soft with her. She has been testing you constantly and found you to be a weak partner, she feels stronger than you because she can walk all over you and she does, you are a door mat. You have no voice, you're afraid to speak up because you think you will lose her but the truth of the matter is, you have lost her already, the process you are in right now proves this, she's just having her fun with you now, seeing how much she can beat you up and bully you. She can't love you or be attracted to you if she doesn't respect you. How can she respect you if you're the man in the relationship and she's stronger than you? How can she respect you if you won't stand up to her when she acts poorly and disrespectful? If you can't stand up to her how could you ever be expected to stand up for her if she ever needed to be protected? You've proven to her that you can't stand up to her so you're useless as a male mate, as a protector, etc.
You let her go, you don't fight to get her back, that's how you snap her head back into reality.
No more funding her "fancy & free lifestyle", tell her to get a job and work for her money and she can buy herself whatever she needs because you won't be doing it anymore.
These are your 180's and you need to start doing this immediately or I promise you that you will be going through this for months/years.
"What is best for my kids is best for me"
Persevere = happily being patient over a long period of time