Ok Ben, here goes...and I will try to not be harsh if I can.
You have been told be many people that it's not about you, or really, your perception of what "us" is. It's all about her and HER perception right now and all these things you keep doing to invalidate her perception are not helping.
As for the condom present, that, to me, underscores that she may be VERY right about some of the things she thinks about you. I don't say that to be mean, but to try to get you to stop thinking that this is something you can fix by using guilt, hard line tactics (keeping the kids from her) or just "willing" it to be different.
What you really need to understand, and I know how hard this is, is that your marriage is over, or at least your marriage as you knew it. The sooner you get that, the better you'll be. Getting that is the difference between fighting to save something that was rotten to begin with and fighting to create something entirely new, starting with yourself and building out.
If you continue to deny the existence of her perception of you, your marriage, your overall situation, your behavior, etc, you will probably not do very well with DB. If you fail to understand that she is her own woman, insane or not (better NOT to take the approach that she must be insane), and she is NOT bound to you or your marriage by a piece of paper, vows, history, kids, your feelings, or anything else. She's figured out that "Hey, if I want to, I can just walk away, and more than that, I may be able to find something...well, I may ALREADY have found something better than Ben..." and she's taking action.
Ok, that's pretty bleak, but here's the good news. You DO have history, not all of which is negative as she'd have you believe, but all this jealousy and bad behavior, justified or not, from you is not doing a damn thing to highlight those "good" times you shared, or the good parts of you that you believe she just HAS to acknowledge (trust me, I know how that feels).
I can't say that your wife will have a change of heart if today you started on a campaign of detachment from her actions/words, self discovery/growth, unconditional love (especially for YOU), and realize that you can't "fix" this as much as you can fix you. What I can say is that it's very likely that she won't have one any time soon if you keep this pursuit/gift giving/jealous public embarrassment up.
Here's the cold/hard bottom line. Your W may leave you no matter what you do or say. You could go into a phone booth and emerge as Superman and she may still see Lex as the better choice. That's why the best thing for you to do is to still go into the booth, become Superman and start by being a hero to your kids and then to yourself. You have nothing to lose. Your marriage, as you knew it, is dead. Start building your life around the idea that by being the best Ben you can be, and the best dad, you stand a great chance of at least getting her attention, if not make progress toward the goal you so desperately want; to save your marriage.
I know you love your W deeply. If not, you wouldn't be here. I also know you've probably heard "If you love her, let her go and if she comes back..." just about one too many times so I'll spin it this way. You don't necessarily need to let go of her, but in order to actually see your goal realized, you may have to let go of your goal to save your marriage for now and work on saving yourself. Without a positive face on your efforts, you are only adding fuel to her fire to leave.
Look man, I KNOW how hard this is and I really think you can do it. Just remember this one thing that has helped me SO much in my efforts; Judge EACH of your actions in relation to her by this simple idea. Will whatever you are about to do help the overall sitch? I don't mean will it make you feel better, or get her to see something you are sure she doesn't see now (BTW, trust me, she sees, she just doesn't care much right now). Will it REALLY help? If not, DON'T DO IT!
I do wish you luck and I will keep up with you. Please try to get positive. It's the first step to real progress.
