Are you both using the stock Samsung Calendar app, or are you using the actual Google Calendar app?
All of the calendars you're using are from Google Calendar, right? I'm talking about Google Calendar in the cloud, not the actual Google Calendar app. And I assume that on the Google Calendar website, you have shared your default calendar with your husband, is that correct?
On your husband's Note 4, open Calendar, and go to wherever it is that you select calendars to display (on the Google Calendar app, either tap the menu button at the upper left or swipe in from the left of the screen). You should be able to see all calendars associated with the Google account, including your default calendar that you shared with your husband.
To make sure everything is syncing correctly, go to Settings>Accounts-Google>[your Google account], and make sure Calendar is checked on.