My pleasure and thanks for following up!
I think the best way to differentiate the two template is to keep the default calendar template (which is already full-width) and override the single-event-php template by adding a sidebar to the template. That could be a sidebar that is already registered in your theme or perhaps a new one that you register specifically for this template.
The Themer’s Guide is a great overview for how to override templates.
Oh, and by the way, there is no need to purchase PRO in order to do this. The free version of the plugin can do template overrides of the same files. 🙂
Cheers!
Geoff