Sync contacts between 2 Apple IDs and multiple devices
This is always a complicated question and the answer is usually a puzzle that boils down to a per/user-setup basis.

Before I can give you a proper answer, I'm going to need some clarification on your setup. I will need you to correct me and/or fill in the blanks on any assumptions I may make about your setup. 

Can you please elaborate on 


  so in my contacts/settings/default account some years ago, I entered his Apple ID.


Where did you enter his apple ID? In your iPhone, on your iPad, iMac, MBAir etc.?
Does that Apple ID continue to be on the device it was originally entered in?

Furthermore, (correct me if I am wrong),it seems like your setup goes as follows:


Your husband and you share a "household" ipad, macbook air, and imac. Then, each of you have your own seperate iPhones. True/false?
On each of your phones, you and your husband are both logged into icloud (Iphone>Settings>Accounts &amp; Passwords>Accounts>icloud address) using your individual "WifeiCloudaddress@icloud.com" and "husbandiCloudaddress@icloud.com" accounts. True/False?
On each of your iPhones, under the "Iphone>Settings>Accounts &amp; Passwords" screen, there are no other accounts that your phone is linked to, ONLY, your icloud accounts. T/F?
On each of your iPhones, under Iphone>Settings>Accounts &amp; Passwords>iCloud>yourname, you have the "Contacts" ticker ticked to on (should be green". T/F?
On your ipad, macbook air, and iMac, under "System Preferences>iCloud" you are logged into icloud as "husbandicloudaddress@icloud.com". T/F?
On your ipad, macbook air, and iMac, under "System Preferences>Internet Accounts" you are logged in with "husbandiCloudaddress@icloud.com" as the primary icloud address, and below that "wifeiCloudaddress@icloud.com" as a secondary icloud address. T/F?
Neither of you are not syncing contacts on any of your devices through gmail,outlook, or any other cloud services are you?


There still may be more details that I need to know but they aren't coming to me right now. If you think of any other specifics (extra accounts/family sharing, gmail,outlook,etc.), please elaborate and let me know.