Hi @David_Di_Pasquale, in order to stop the video from playing when the modal window closes, you are going to need to a modal controlled using jquery instead of an interaction. That would be my first suggestion. The interactions will set the css to display or hide the modal window, and set opacity, but does not control the video itself, thus the need for a little jquery.
Here is a topic on creating a modal window that you open and close using a little jquery:
and here is a topic that talks about stopping the video when the modal is closed:
If you get stuck making this, let me know and I am happy to help further.
Cheers, Dave