Hi @DeboraG,
Thanks for reaching out.
The width is taking the value set through the Theme Options > Layout and Design to Site Width and Site Max Width. I would suggest you increase the value of Site Max Width and set 100% value to Site Width to get the full width page.
The Single Event page template is coming from the MEC plugin, and modifying the Single Event page required customization. I would suggest you hire a developer who can assist you to do the customization or you can avail of our newly launched service called Elite service, where we offer complex customization
Thanks