Hi Razvan
Sorry for the delay, this has been a nice and long debug. But I finally have an answer.
First of all, the Beaver Builder theme, and hence its child theme, is only supposed to provide full width layouts for Pages, not for Posts or custom post types. That is why you get that in the frontend. So, in short, the frontend is right.
Now, why do you get a full width row in the backend? Well, that is a little more complex to explain, but I will try.
Our integration has to "fake" the PHP template that is going to be used in the BB frontend editor. As you know, when a Content Template is assigned to single posts and archive loops, you can select what kind of preview the frontend editor will ofer. Whe assigned only to single posts, we make that selection for you, defaulting to the theme PHP template for single items on that post type.
Then, and this is the tricky thing, we scan those PHP templates to check whether they actually render the content of the post, so they can actually render the BB frontend editor. Here comes te problem: the BB theme, as many others, do not display the content from those PHP templats directly, but they include another sub-templates that do that part. Because of that, our integration discards those PHP templates and applies a default one we include in our side.
That default one is a barebones PHP template, hence it does nto have the restrictions of the BB theme regarding posts that are not pages not getting full width rows. So in the frontend editor preview, you see our default PHP tempalte, with full width rows, but the theme in the frontend uses its own PHP template, which does not allow for them.
What we can do is limited here. We can not provide the theme with support for full width rows on custom post types, but we have a ticket already as to support themes, like this one, that use sub-templating for displaying the content. This way, your preview will matc the correct frontend outcome that you are having.
You can kind of sort this unexpected outcome by simply duplicating the page.php template in your child theme and remaing it to single-slug.php, where slug is your custom post type slug. There will be other issues, like the single post title appearing around, but if you can tinker with the PHP template a little this can be also solved.
I am sorry I do not have better news, but at least now we knwo what is happening here.
Let me know if I can assist you with anything else.
Regards.