How can I permanently remove the irritating copilot icon from my word document

I think you are looking for this support article: https://support.microsoft.com/en-us/office/turn-off-copilot-in-microsoft-365-apps-bc7e530b-152d-4123-8e78-edc06f8b85f1

Note the instructions below only work for the client apps. You can not disable the icon in the web versions.  Here are the instructions:

Clear the "Enable Copilot" checkbox on Mac devices

1. In your app (for example, Word), select the app menu, and then go to Preferences > Authoring and Proofing Tools > Copilot.
2. Clear the Enable Copilot checkbox.
3. Close and restart the app.

Also you should note that if you are using an external mouse you can right click on a Mac.  You just can't from the trackpad easily.  Hope this helps