You can use Microsoft Flow for generating a PDF file based on a SharePoint list item:
Not really all at once. To stay within support boundaries you need to use the API. What you could do is to restore DB to non prod environment and use direct SQL queries to the DB to get the data you need. The right SQL queries can be figured out with the SQL profiler.
There are some options for your reference:
Use "Save list as template" and include content, then upload to destination site list template, then create a new list using this template.
Use Third-party tool as ShareGate to migrate the list.
Reference: Copy a List in SharePoint or Office 365
Use PowerShell and CSOM to go through the source list and add items ...
Here you have an example how to do it with BlogML
Now using PowerShell should be feasible as well. You don't need to have specific one for Blog. Blogs are essentially list items. So you need to look a script to export list items. (depending on columns you use you should on your local ...