these all seem weak factors.

Indeed, and moreover they cancel each other out.

the fact the the Republicans have gone so strongly anti-science is certainly a bad sign.

Only in their rhetoric, which is at most weakly correlated with their actual policy decisions.

are the things I should care about in the election, or can I just lie back and enjoy it as a piece of interesting theatre?

Pure theater. Enjoy the show. Think of it as the Status Olympics, which occur every four years along with the summer games.