I laughed when I read the quote at the top of your post. Thanks, Phoebe! I needed that. And thanks for the compliment too!

I suppose I did spend several years trying to understand my wife, and it finally started to come together since early this year when I started to learn about BPD, but that's another story.
I think you're right about it being my place to provide the majority of emotional nurturing for our daughter. I realize it can be a lot to ask of some with BPD, so at least I just want my wife to mess up our daughter as little as possible.
My wife does teach her other things. I love watching (or overhearing) them draw, paint, bake, or anything else. It just seems to happen rather infrequently and inconsistently. And sometimes it ends when DD does/doesn't do what she is/isn't supposed to do, or "doesn't listen". To me these seem to be age-inappropriate expectations. In a few cases they have not resumed a particular activity in months because my wife has not gotten over what DD did. My wife seems more likely to set DD in front of the TV with several movies each day, while my wife watches her own TV shows, reads, or surfs the web.
She does show an interest in DD's learning development. The one book I recommended that my wife actually started was one on expected development for DD's age. Some of the things my wife does are great. Unfortunately I think she approaches others as too much of a structured lesson rather than play. Not surprisingly, DD loses interest after a little while, and then my wife lectures her for "not listening".
DD wants to help mommy pretty often with all sorts of things. Unfortunately, rather often this triggers my wife to want some space.
I am glad that my wife takes interest, while in other ways I suppose I am glad that she removes herself from some situations that would trigger her around DD.
I just hope I can help my wife learn to be a bit less invalidating towards DD. To a reasonable extent I've learned to accept that she is who she is towards me, and only I can control what I do in my part of it. But I suppose I'm still hanging on to some hope that she can learn better ways of interacting with DD, since DD is unlikely to learn at age 3 what it took me almost 4 decades longer to learn.