I received your email about the PHP errors you were getting. I suspect a number of things won’t work as they should until we fix that issue as it’s fairly critical (your directory path to the Microthemer plugin folder is incorrect on your multi-site install – it’s an URL instead of a directory path). Can you style anything in fact?
I’ve replied to your email so we can discuss troubleshooting options there too if you like.
PS double-clicking a video embed might be problematic anyway. The solution is to double-click something near it (it’s parent element perhaps) and then navigate onto it using the DOM navigator controls. The DOM navigator can be accessed from the ‘Inspector’ tab of the advanced options on the selector wizard (top right after you double-click something).
Also, you need to double-click without pausing too long between each click (more than 700ms). Microthemer allows you to single click links and buttons as it’s useful to follow them sometimes.