The best thing to do is let WordPress do the CMS stuff with posts/pages/etc, and add advanced features using either plugins, custom templates for certain pages, and/or use the shortcode api. For the linked page, you should have it as a page, and use a shortcode to load the custom form in. As soon as you start trying to combine non-WordPress things you will run into inconsistent and 'interesting' behavior.
Dependency wise, at the moment the
bcn_breadcrumb_trail class depends on WordPress (or rather functions provided by WordPress and the