How do I insert content of various MySQL fields in post?

I also would vote for creating a short code. The shortcode code could pull data from a database/table, and ‘build’ the text you want with values from the table.

Lots of googles on how to build shortcodes – check those out, vs me putting some sample code here.

You would put the shortcode function in your Child Theme’s function.php file. (You don’t want to put it in your main theme, as any changes to the main theme’s function.php would get overwritten during a theme update.)