Glad you like the plugin!
Yes, you can hardcode the form into the theme. In fact, that's how we would expect most people to use it. You can use a conventional WordPress template tag:
or you might prefer to use:
do_action( 'facetious', array(
as this won't cause a PHP error if the plugin should ever be deactivated.
One of the options you can specify in that array of arguments is
id: that would allow you to target the Facetious form in CSS.
The widget has a class
facetious_form, which you could use, perhaps in conjunction with an ID for the particular sidebar.