How to remove my Mac from iPhone call audio routing list?
Try allowing all devices and then disabling Mac specifically in the "Calls on other devices" settings you posted. 

Open FaceTime-> Preferences on Mac and uncheck receive calls from iPhone checkbox.

On the extreme, if you don't use continuity feature, (didn't see it in the question), could you turn Handoff off altogether in iPhone and/or Mac? It is in Settings -> General-> Handoff on both devices.  Either of the devices could be at fault. So check all combinations.