Odd that your scores don't have a 'below average' class? Apart from that the principles are straightforward enough and the text reproduced using bookmarks populated from the combobox. See attached. The principles can be extended to other dropdowns in the same document by adding more case statements to the macro as appropriate.
When working with content controls, you should find https://www.gmayor.com/insert_content_control_addin.htm useful.