I would suggest that if you want a good and wonderful marriage, then respect is key. Have someone observe the couple and watch the dynamic. I wonder how much of the various graphs could correlate with likelihood of respecting the other.

I am surprised by the length to proposal. My opinion is that once you meet someone that really clicks, then it works out quickly and well. I wonder if there is another dynamic that correlates with the religious as well, one that perhaps is more in the vein of arranged marriages, so to speak.