How to install and set the theme:

Go to Edit -> Preferences -> Themes -> Click install and locate the xml file that I included. 

After installing the XML file, please click the drop down to the left of the "install" button and set it to the new theme :)

How to setup the startup file:

First off just in case i would prefer that you have the latest version of blender (or at least 4.1). This ensures that there are no options selected that don't exist in previous blender versions. 

Open the startup blend file that I linked and go to File -> Defaults -> Save Startup File

Congrats you did it! I hope you guys like both the theme and startup file :)