Hi,
Do you happen to be sharing an Apple ID ?
As a result do both of your appear on the My Card in the Contacts app ?
In Messages your can not enter your own Name in to "To" spot as the My Card is not called up.
You are not expected to call yourself.
If you want to test between your Mac and your iPhone then you must enter the iPhone number in full.
If the My Card and your wife's card have the same Apple ID the Contacts app will not be able to work out which card is needed.
7:42 pm Saturday; October 20, 2018
iMac 2.5Ghz i5 2011 (Sierra)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
MacBookPro 15" 2016 (High Sierra 10.13.x)
Mac OS X (10.6.8),
iPhone 6 iOS 11.x and an iPad (2)