You don't have to experience childbirth in order to be a medical doctor experienced in the medical aspects of it. In fact, until recently, most OBGYNs have been male. There is all sorts of research out there... experience is not research. They know the conditions, how to diagnose, implications, and treatments. I'll bet your primary care provider has not experienced all his or her patients might have. And an oncologist does not have to experience cancer in order to be an expert in cancer.
As for marrying within culture, I believe that the verse "do not be unequally yoked" is much farther-reaching than just the couple's faith. In fact, social psychology studies show that for most people, "birds of a feather flock together" is more true than "opposites attract." Opposites attract for a little while, but do not make good lifelong partners, which could be part of the reason there are so many divorces. The more alike you are to start with - culture, class, race, education, family type/structure, parenting styles, patterns of thinking, etc... those are all part of being equally yoked.
If you think of "the two will become one" - it refers to a process of becoming one. The more "one" you are to start with, the easier and shorter the path to really becoming one is. But if you start at opposite ends of the spectrum, it is that much more challenging and further a couple has to travel in order to become one. If you start on the same page, much easier. If you're not even in the same book, it's hard to get on the same page.