So, instead of switching to Hemingway as a new theme, I just made some small tweaks to Sandbox and my accompanying CSS. I've been happy so far to be able to do my customizations to Sandbox entirely in an add-on CSS - but this time, I wanted an additional WordPress Widgets sidebar. Sandbox offers 2, but I wanted 3. A small hack, but one I'll have to remember to re-hack if ever I update Sandbox.
Anyway, I think I've got a start on what I really wanted from Hemingway: The sidebars are now footer columns, and the body of the blog itself is much simpler. Now I can dump even more of my aggregated net-activity into the footer, which will be there for people who've stayed with the page long enough to get to the bottom and possibly want to see more of my drivel.