Hemingway Rewritten – looks all wrong in IE9 or earlier

Our blog, https://www.recordoffice.wordpress.com, uses the Hemingway Rewritten theme. I took a lot of time to get it looking right, checking it with colleagues and so on – only afterwards did I realise that it looks perfectly horrible if viewed with IE9 or earlier. Does anyone have a fix for this? (To answer anticipated questions, we don’t have any plugins and I haven’t been tampering with anything “under the hood” because I wouldn’t know where to start!). Thank you.