breadcrumbs trail from page to category to post

It sounds like you want to use pages instead of the category/term archives that WordPress normally generates. The best way to do this is to map a page to your category (use a term meta field) and then replace the URL appropriately everywhere in your site using the appropriate filter (look for something in get_term_link), or just target the URLs in the breadcrumb trail by using the bcn_breadcrumb_url filter (https://mtekk.us/archives/guides/link-to-a-page-rather-than-the-category-archive-in-a-breadcrumb/ is a quick primer on how to this filter).