These are the facts in your sitch:

W is playing you, big time.
You have not detached. You MUST do this immediately.
You are still meeting her emotional needs. Stop it. Now.
No physical contact. At all.
No staying overnight.
No $$$ from you. This takes away from your real fam (you & kids)
Stop talking to her except relating to kids at the exchange
Cancel concert
NO MORE DATES, DINNERS, ETC. NOTHING!
Deny her your company
In fact, I would suggest going pitch black, except for kid exchange.
During those times, do not initiate any convos at all.
Give brief, one-word answers to any of her attempts to engage you.
Do not defend or explain anything at all to W.
Stop tipping your hand.
GAL and socialize with anyone other than W.

You are not taking this seriously and you really need to. You are early in this mess and are making it far worse each time you come in contact with W. That is because you, for some reason, refuse to detach.
Plus, you seem to think there is a magic bullet, or something. There isn't. This takes a lot of time. A LOT more than just one month.

Cancel the concert.