My IC pointed out to me that rescuing and fixing behaviors are actually controlling behaviors... and, yes, very much like a parent. At some of the worst points of our sitch, my H would accuse me of being like his mother, which hurt so deeply. His mother is a person who has huge anger issues and is not very emotionally healthy. Never, in our 19 years of M did he ever before accuse me of this. I talked with his sister about it at the time and she was appalled, as her perspective is that, personality wise I am about as different from their mother as anyone could be. OW is actually much more like their mother. But, in talking since, my H was able to say that he was feeling like I was "mothering" him at the time. Very different!
Anyway, it is part of my own journey in all this to stop that, detach more. But, Rabbit, as you said, in piecing you can't totally detach... and finding that line in between is tough. Still struggling there.