Stop messages to my new iPhone from appearing on my old iPhone
You need to disassociate your Apple ID from iMessage on his iPhone. You can do this by following the steps outlined below. Don't worry, iMessage/FaceTime account settings are separate to iTunes account settings (so you can choose to have different Apple IDs for each)


Open the Settings app
Scroll down to and tap 'Messages'
Scroll down to and tap 'Send &amp; Receive'
Tap 'Apple ID' (which should list your Apple ID)
Tap 'Sign Out'


This will disassociate your Apple ID from iMessage on that iPhone and still leave it intact on your new one. Your husband will still be able to send and receive iMessages using his number. You will probably want to do the same for FaceTime too otherwise he will receive FaceTime calls for you and vice versa!