OK, my last words on content templates.
I do not understand what you mean when you say your design "blows up" when you use templates.
I followed your instructions (https://toolset.com/forums/topic/taxonomy-filter-by-page-it-is-shown-on/#post-1224039). Presumably you meant left sidebar, not right sidebar.
7. click the 1/1 container - that would be the header container.
Header? It's just part of the content.
I edited this post, using Fusion Builder per your instructions: hidden link
You can see the backend in the screenshot "no CT - the post.png". Note that no Content Template is selected.
You can see how it looks on the frontend in the screenshot "no CT - front end.png". Everything inside the red box is "the content", in this case designed with Fusion Builder. Everything outside of the red box, including the actual header all the way down to the page title, as well as what's below the red box, is output by the theme's single.php template. (This is a single introduction post.)
Now, before, I had created a content template for introduction posts, which you can see in the screenshot "with CT - the template.png". The template is designed in two columns and inserts various fields from the current post, such as the featured image, as well as the content of the post itself (marked in red) using the wpv-post-body shortcode.
If I assign this template to the previous post and display it on the front-end then the results are that the content area when no content template was used has now been replaced by the design from the content template (with CT - front end.png).
The outer square shows the area replaced with the content template, and the inner square shows the part of the template outputting the post content.
Otherwise, everything, the header, the footer, the "design" etc., look just the same between the two versions.
Anyway, we are giving up here. I'll continue in the other thread.