That's just it. I don't feel like she's enforcing it, and at the end of the day, she's letting the kids do whatever they please. I overburdened my daughter with my feelings, I get that...but what more can I do to get my kids over here to spend some nights?
Just be the rcok. Be happy being alone. I can do this - but I don't feel like it's going to change anything with my kids and I, guys
Apologize. And not a back handed apology. A real apology to both your kids, and W. Tell them you've seen the error in your ways and will be working with your IC on emotionally burdening your kids. Then have a conversation with W. Tell her that you understand why she doesn't want to force it and you acknowledge that you haven't been super dad. That you have work to do and you're ready to put that work in. Then ask her what does she need to see from you before she can feel confident in telling the kids they don't get to run the show on visitation, that you and her run the show.
W regardless of how this marriage fell apart seems to be pretty level headed when it comes to the kids. If you could actually make it about the kids. And face time with the kids. And quality time with the kids. And not about your needs. Your wants. You winning. I'm sure she'd work with you. But this involves you being the bigger person even when you don't feel like it or feel like W deserves it. You may have to do some sh*t eating to reach your goal here. If you have any questions about sacrificing your ego to do so I suggest you look at the dog pile of comments above as to why no one cares about your ego when it comes to your kids.
Last, kids are kids, and are fickle by nature. And my god, teens and tweens, holy h3ll, there isn't even a word for how volatile their emotions are. If you read the book and you've seen people like Steve85 talk about how DBing has helped change their relationship with their teens I think you need to maybe look into applying the same principals there. Find another board like this one about parenting through an S/D when you maybe weren't the best dad in the world all the time. There are boards for everything these days. You need to own ALL your mistakes with these kids, not just the recent ones. You need to lower your expectations of your children. They are not required to love and like you they way you are to love and like them. Unchien's suggestion of co-parenting classes is top notch. I still strongly suggest family therapy with just you and the kids. Maybe just you and D first and S will follow as he seems to. You really really really need to let go of the idea that the relationship with your children is something that is just supposed to exist with out any work. They aren't babies. Their needs aren't food, touch, stimulation, and medical care. At this age it's like a real relationship that needs development and work. And you are the parent, it's not their job to cultivate this relationship. It's yours. It's always going to be yours. Even when they are in their 30s.