... W was happy to see girls when we arrived, but distant to me. After we had been home for about 15 minutes: W: "Why didn't you call back?" M: "You mean on Saturday?" W: "Yes." M: "You didn't ask me too." W: "I said I was calling to ask how the girls were. That means I want you to call back." M: "Sorry. I misunderstood."
Hand slapping time.
She said she was calling to ask how the girls were and that means she wanted you to call her back?
Didn't you just tell her that she didn't ask you too?
And then you apologized to her for not understanding?!
Why?!
What did you do wrong?!
If she wants you to call her back, she will communicate that to you, she will be clear about this and any other communication in the future because you are not a mind reader concerning her or anyone else.
Make that clear to her the next time you speak to her. You tell her "... I was thinking about our conversation where you didn't ask me to call you back but I was somehow supposed to read between the lines that it was something you wanted me to do - I don't read minds, next time if YOU need something from me, just say it in plain english, I won't apologize for not reading your mind and knowing what your exact intentions were."
Don't be angry, you act calm, assertive and make eye contact with her the whole time.
You apologize way too much, she's having an affair, I don't see her apologizing about it every time she sees you!