Your comments

You may want to consider creating custom CSS classes for the elements you're trying to target. You can easily add these inside the editor using HTML text. Or, you could consider creating a custom page templates for the themes themselves. I'm not sure what you mean by "CSS options". BoldGrid does not place any limitation or specific options on the level of customization you require.

Hi David, I tested the CSS and it worked. I was able to see the background image just fine. Are you using a dot before entry-content, like this: .entry-content? If not, I'd advise adding the dot for correct CSS syntax.

I'd suggest taking a closer at "All in One WP Security" and "Blog Designer - Post and Widget". The former because security plugins often introduce a variety of functions that can range greatly in how invasive they are, some can actually tamper with file permissions (which could cause database connection errors if they affect the config file), and the latter because another design plugin may interfere with BoldGrid.

Likewise, I'd consider double-checking "AddFunc Head & Footer Code" to see what this plugin is adding to the header and footer. I noticed you also have "GA Google Analytics" installed. It's possible both of these plugins are adding extra code to your files (which could potentially cause code conflicts).

If you want to go even deeper I'd recommend duplicating your site in a local development environment and use something like XDebug to debug your PHP. This is the more advanced option, but debug information will provide more detailed errors and indicate which files precisely are causing problems.

I'd recommend targeting the element using your browser's developer tools. That way you can try CSS code live.

We've never seen any evidence to suggest that private domain registration will affect search engine rankings.
The staging site is considered a new canvas, where you can create new content or copy over what you like from your active site. This way, you can create new content in the staging area and launch it as active when you're ready. For this reason, the sites do not mirror each other.

Do you have any debug information available? A clear error message may indicate whether the issue is in the theme files themselves or somewhere else.

This is likely the result of a setting in WordPress itself. You will want to check the Site URL and Home settings.

Yes, it is possible to edit the HTML for the page content using the WordPress text editor. You can also use the preview to make sure your edits are getting you the desired effect. If you make an edit, save it, and don't like the result, WordPress revisions let you roll back to a previous version of the page.

Yes, you certainly can add BoldGrid to your site just as you would any WordPress plugin or theme. However, BoldGrid tools work best with BoldGrid themes, so adding the drag and drop features to your current theme may not work as expected. Ideally, BoldGrid can be used to build a new site in the background of your current site. Then, you can launch the new site when ready.