Unanswered and mostly unasked

I have a book on public opinion coming out in September 2020.  Although there is a lot of good research on public opinion, some of which I discuss in the book, I've come to think that there are a number of basic questions that are not only unanswered, but which are mostly not even asked:
1.  Why have the effects of higher education on opinions changed?  Most people who follow politics are aware that college-educated voters have shifted towards parties of the left, and less educated voters have shifted towards parties of the right.  This is usually attributed to the growing importance of "social issues" (understanding "issues" in a broad sense), on which education goes with more liberal opinions.  But educated people have also moved to the left on at least some economic issues (see this post for an example).  Why?  I haven't seen any efforts to explain that movement, or even a clear recognition that it's happened.
2.  Why are their no major parties or politicians that are conservative on economic issues and liberal on social issues, or liberal on economic issues and conservative on social issues?  In the general public, opinions on social and economic issues are almost uncorrelated:  there are a lot of people who are to the left on economics and to the right on social issues, or vice-versa.  So you'd expect some politicians to appeal to these groups.  There have been lots of predictions that this will happen, or claims that it is already happening, going back to the 1970s, but so far it hasn't.   I've written about this in this blog, and Paul Krugman has discussed it in his newspaper column, but I haven't seen any discussion in the academic literature.
3.  When do the effects of different influences on opinion simply add together, and when do they combine in more complicated ways (interact)?  It's not unusual to find interactions.  For example, here are the percentages agreeing that people should have to get a police permit before buying a gun, broken down by race and gender:

                        Men          Women
White                67%            81%
Black                77%            85%

The combination of race and gender is more than the sum of its parts.  Gender differences are larger among whites than among blacks, and race differences are larger among men than among women.     There are lots of studies that look at interaction effects on specific opinions, but I haven't found any efforts to generalize about when interactions do or don't occur.
4.  Why are there long-term liberal trends in some (but not all) opinions?  There are a lot of questions on which opinions show a liberal trend over fifty or more years, but very few which show a conservative trend.  Looking  back over history, some "liberal" trends seem to have been going on for centuries:  for example, increasing support for the principle of gender equality.  In everyday discussion, people are well aware of this: a popular definition of a conservative is someone who wants to stop change or "turn back the clock."   But among intellectuals, claims that there is any tendency for moral progress have come to be regarded as naive or worse.  So there are few attempts to specify or explain the trends.  Those attempts tend to be by people who have a "grand theory" into which they try to force everything, so it's easy for specialists to ignore or dismiss them rather than trying to refine or improve on them.* 


*After reading Steven Pinker's The Better Angels of Our Nature a few years ago, I wondered how it had been received by sociologists, so I checked Contemporary Sociology, the American Journal of Sociology, and Social Forces, and found that none of them had reviewed it.  There was a review symposium in Sociology (the journal of the British Sociological Association), but only one of the four really discussed the book--the others were just expressions of indignation.  Claude Fischer gave it a serious review, but that was in the Boston Review, not a professional journal.