Hi @Tluchini
Be sure to remove the Blaze from your account before handing it over to your husband. While he sets up, your Ionic should be out of range (25 feet or more) so he can set up without any problems.
The history is retained on the servers, with your own email and password. It isn't stored on the device.
He may see burned calories, but that's normal when setting up a new device.
Now you two can do challenges together. That's awesome!
Let us know if you need any further assistance.