macOS Messages – How to Disable Rich Links

The simplest solution is to contact Apple Support (as this article makes clear) since they actually have engineers that can modify which devices and phone numbers are associated with your (or another's Apple ID).

So, just contact Apple Support.

My experience is you cannot actually delete an iMessage once and have it delete elsewhere.

You can only delete the local cached copy of a message to suppress it being showed/stored on that one device. If you turn off iMessage and turn it back on, you will see the messages from iCloud come back whether you deleted a message or not.