Longer reply later

This is a great subject. I'm pretty tired now, too tired to give a thorough response, but I'd like to make one at some point.

The immediate impact on intergen relationships would be small, or not really publicly noticeable, at first. In fact, a "realistic" (since that's what you're going for) implementation of Epstein's competency testing would be a gradual thing, applying to successively more areas. Examples: driving a car (that one already exists on some level), being eligible for certain types of employment, ability to test out of any number of high school grades and receive equivalent diploma, buying tobacco/alcohol, etc. Later on the age of consent restriction and full emancipation might be on the table, but people aren't gonna go for it until young people prove that they are capable to act responsibly in a variety of domains.

When parents start recognizing that their 11-18 year old offspring can handle a lot of stuff just fine and take more ownership in their own lives, then they might start to believe they can make their own decisions about sex. This could take quite a few generations after the other changes are implemented.

I can see some of the angles you're touching on, though.. more thoughts on that later.