The new Facebook Page Plugin was designed to be responsive from the start: you can define a width parameter when generating the Page Plugin from Facebook Developers’ site, but that width value will be overwritten by the width of the Plugin’s parent container. You can read more about it here:
https://developers.facebook.com/docs/plugins/page-plugin#adaptive-width
In practice, this means that you don’t actually need to define a width value, as long as your theme defined a width value for the container around the widget.
If you’d like, you can let me know your site URL and I’ll give you the necessary CSS code to add to make sure your Facebook Page Plugin is displayed properly.
If you want your site URL to remain private, you can also contact us via this contact form:
http://jetpack.me/contact-support/
