Well, I think you need to sit down and tell your wife how you feel. I think you need to do this in a way that demonstrates that you are miserable, for yourself, and for what has become of your relationship. Replace any anger you have with sadness at it all. I think that you need to ask her to listen and you also need to offer to listen to her. I'm no expert, but you can bet your bottom dollar that she also feels hurt, or dissatissfied with life, you need to be there for her, and you need to let her know that.
I might have this all wrong. You might look at what I've written and think that I am out of order; commenting on your life and making assumptions about what you should do, and how your wife feels. That's fair enough, and you can tell me its none of my business if you like. I won't get offended.
Anyway, I hope you can sort things out; its not easy mate but I look at what you've written about seeing to the kids before you've even had a shower and teaching shoelaces, the time and doing the weekly swim and I stand you against blokes that haven't seen their kids in years and cheat on their wives and all the rest of it. You seem like a nice enough bloke to me and we all have our demons, but that doesn't make you a bad person.
I hope you work it out, the both of you.