How to delete "reachable at" email addresses?

Nobody can misspell your name in those addresses. As those are created by you, and only you. So if its misspelled its because you misspelled them when you created them at some point.

Generally if you had a @mac or @me address those are automatically assigned as aliases to your Apple ID.

Otherwise, make sure you don't have any aliases created for iCloud email: Use email aliases on iCloud.com - Apple Support

Interesting. Outside of contacting Apple Support again, there's no way to fix it from your side.

Its possible they fixed the underlying email address, but the display name might have not been corrected.

If they have a question mark, you can't delete them. You can't remove/change @iCloud.com, @me.com or @mac.com aliases.

You are welcome.