Ok, after some fiddling I now have the home page rendering as I want it to on tablets. First I experimented with the viewport setting, but that did not fix the problem. Next, I downloaded the CSS and uploaded a copy to my server. Then, I experimented with the @media setting, landing on auto for the left and right margins and max-device-width to 1024px.
Now the home page renders centered on my iPad Mini, Nexus 9 and iPad Pro. It actually renders the best on the Nexus 9.