I have read quite a bit of what you have shared and sometimes in a situation like this the obsession isn't REALLY about the other woman you hardly know, a lot of times when a man's wife is expecting the first child they can begin to feel anxious about how much MORE of a commitment they are making. So, this other woman could very much simply be a symbol of "freedom" and an escape more than being "the one".

You sound like an individual that prefers to not get so involved with emotion, but DO something active instead. Your wife was "active" with you and may be similar where she too prefers to be active instead of emotional and the way she was active was extremely important to her sense of well being. Without this active outlet she is getting angry and sulking and while being pregnant is doing something, it also can ADD a great deal to someone's insecurity. Actually, IMHO, her comments about being a single mother are not meant to hurt YOU, instead she is expressing a very real fear she has. Her also saying you don't spend enough time with her is again expressing this same fear of losing you and being a single mother. Anger is often FEAR. This ankle surgery caused her to lose something important to her and it was something she used a lot instead of the "emotion stuff" and probably like you, it's her weak area also. And neither of you noticed that because you were both so physical, even sexually. An ankle is a very important part of the body to a person who is physically active (thrives on motion). Someone who runs a lot, jogs a lot, bike rides a lot, all can be a huge wipeout if the ankle is no longer functioning correctly.

Well, now she is several months pregnant and doesn't have that physical outlet so she has two BIG things that can create "fear and anger" and if she struggles with emotions, that would come out very similar to what you have been describing. And you don't do well with emotions either so you want to "escape" which as I mentioned, is something this "other" woman you don't even know symbolizes, "the escape".