If he wants to skip visitation, let him.
I like your plan for his last minute changes during visits. No back and forth. She stays or she stays away.
It has been my experience that sometimes the child is used as a means to maintain a relationship between ex partners. Like my ex wanting to make plans that included me, so he could visit with me while visiting our daughter.
This includes my trying to force my ex to be an active parent by reminding him of special dates and events. I need to remember he is an ex partner and allow him to keep his own system of reminders.
I also had to learn not to engage in social banter with my ex. We were life partners and shared everything. Learning to find other outlets for venting and sharing about my day was a learning process.
In the end, my ex has very little to do with our daughter. It is an adjustment. I make sure she understands that she is not the reason for silence from dad. She is loved and appreciated. Our home is filled with love. I don't miss feeling responsible for making another adult behave like a parent.