I hate the saying "things happen for a reason" too, sometimes.
But look at the positive changed. You are taking a more active role in your D's life. You are taking her to her hobbies and if you were still with your wife, you might have never been involved. Becoming a more active father could be something very wonderful coming out of this. I see a lot of men on here who admittedly weren't the most involved fathers before BD. Yeah, it's a shame it took such a think to realize they should be a bigger part of their kids lives, but it may have never happened otherwise.
You are doing stuff and getting out of the house which is good.
Focus on your kids. You haveto get up, out of bed, be engaged, do things because you are a dad and you have kids to take care.
Trust me, you would not want a hostile coparenting relationship especially with children that young. An amicable co=parenting relationship is not one you should hate, it's one you should appreciate. Why? because it is best for your kids!