Generally speaking, longer pages tend to perform better. This is likely because Google is increasingly using semantic analysis on the pages and a longer page is statistically more likely to contain the semantic phrases which Google considers relevant to the topic and to search intent.
A common practice however -- whether you subscribe to this SEO theory or ...
I would say that exactly what you want to accomplish is not possible.
Here is some useful information for you.
# and whatever comes after is never sent to the web server, and therefore .htaccess doesn't have access to read it.
What plugins are you using? Some plugins like Yoast will automatically use the Article schema for any blog post. I'm guessing that you probably have another plugin that is also adding schema objects to your content.
Try disabling all of your other WordPress plugins and rerun Google's Schema tester. Then add the plugins back in one at a time, and re run ...
You seem pretty knowledgeable, have you disabled .htaccess?
Tried a dummy index.php with just something like "test" and nothing else so you can see if you are actually reaching the site? (That's the first thing I would do)
The best (only?) way to do this is using a subdomain e.g. new.example.com. In WordPress create your account using the subdomain. Find the A Record for this new site, here's how: https://en.support.wordpress.com/domains/custom-dns/#viewing-your-dns-records
In your current hosting create the subdomain new.example.com and change the DNS to point the A Record ...