thanks, marc. i was able to explain the problem to the client and they accepted one of my solutions. i told them that if we were to stack the data to begin with that all devices would look the same, and labels with data cells would have ample room to display.
Inserting the style sheet directly into a Mailchimp text edit box works, but Android is still not managing well. And the table data stacks on some desktop and Apple devices. An interesting situation!
I found this page, http://alijafarian.com/responsive-html-tables/. The thead and th labels were helpful. But only on Apple devices. I still see a problem on Android. Is anyone aware of a fix?
Here's the Litmus test for the table fix I mention directly above