I'm in the same situation. Sometimes flirty behavior, etc, but all signs point towards D still. And also, yes, the slightest regression is a massive failure in her eyes, and validation for why the D is still the right thing to do. I think you're doing the right thing. Stay strong through the 'down' periods when you feel like throwing in the towel.
I got zero contact from her this week, though, except for some kid related stuff. And even that she's dropping the ball on, not communicating back if it's not urgent.
Me: Mid 40s W : Early 40s M:11 T:13 S, D, both 7-10 BD : 11/2017 Separation : 1/18