Hello and welcome, Unsureman
Of course you are being hard on yourself. Try not to be. Its completely normal to not know how to deal with this. It's not part of human training, and there is of course the overwhelming need to keep the family intact. FWIW you did a great job pulling her out the hot tub. Yes the followup is a bit later than you would wish, looking back. However you are doing it now that you have your bearings and you have fresh information. That dance floor scene !
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You are doing very, very well and so far you are making all the right moves, given your stated priority to get proof vs preventing further trysts on her part. That horse has already left the barn, and I'm assuming you are done with her once you get confirmation. Is this correct? I think it is worth extra effort and resources getting the proof. Not that it's strictly needed of course. She is without a doubt currently cheating, and you of course have several strong lines of evidence indicating this.
In my time here I've observed there are two main scripts here that yield results for betrayed spouses. Both require some emotional fortitude in this hurricane of emotion.
The first strategy and the one you are going for currently is the "stealth intelligence gathering approach". This what I did. As it happens and as another poster has commented, I used a cover story for my upset and odd behavior during this time (mine was work upset and adjusting to a new medication).
The second successful strategy used is total shock and awe. No empty threats, divorce papers drawn up and presented, even having them filed and served to WS. Let them believe they have absolutely nothing to lose by cooperating. This cuts through a lot of trickle truth BS. (Paradoxically, this 'filing and meaning it' approach works very well in getting cheaters such as your wife to discover Jesus very quickly and want to fix things.)
The strategy or lack thereof and the one most follow is much less productive but totally understandable given the BS is still reeling. That one you already know. Shock, weak confrontation, and accepting some minimizing bullshit in the hopes that it was a one-time thing that will never happen again and life can go back to normal. Of course most often only the tip of the iceberg is ever seen and the behavior patterns (i.e. cheating) resurface 6 months to a few years down the line if they ever ended. Sound familiar?
Now, once again you are doing very, very well! You are an intelligent person and some part of you has, perhaps subconsciously, prepared for this moment. That being said, I have a few observations for your consideration:
1. She is totally on to you knowing about her cheating on you. This is obvious from your behavior and remarks towards the swinger other couple, the movie infidelity, the dance venue, ect. Also, it is highly likely that the drunk informer's wife knows what he said and has passed that info onto your WW. There is no chance she does not know about your wife's A with swinger couple, that's how drunk guy knew. This has implications for stealth intelligence strategy implementation. Still that's your best bet if you can keep it together emotionally. At some point as you've said you will need to move to confrontation but more on that later.
2. The the intoxicated informant will very likely also become an informant for your WW via his wife. Assume that any info or behavior you let drop to him will go straight to your WW.
3. If you have a plan for more than one eventuality you will feel better. Consider what you will do if you don't get smoking gun info or a confession soon. You are well within your rights to divorce knowing what you already know. Plan for this. Consult with an attorney so you are informed as to how the process works and financial considerations.
When you do confront, have your 'if/then' scenarios already in your head, and deliver in an unemotional calm fashion. Make her do the talking. And of course have surveillance set up everywhere so that you can hopefully capture her following conversations with her enabling friends/affair partners.
I've written a book already brother but one last thing that bothers me is that cookout. At first I thought it was an opportunity to get more info from the informant, but OM is going to be there
. Just the three husbands? I know I couldn't handle that scene without being totally obvious. Do you know how the planning went down? Are OM and informant tight? Best case scenario was if informant wanted to get you alone and then the OM went in for his own reasons. Otherwise who knows? Hell maybe one or both will approach you to join their swinger lifestyle!
All I will say is if you do go then go late so that they have time to get a few beers in them first so you at least have that advantage. I suggest bailing if the OM is there. That way lies madness.