How do I reverse a merged account with respect to two emails, one was the primary and the other was a subaccount?

I cannot access my subaccount emails after merging my primary email with my husband's in an attempt to access is subaccount to change the password I set up for him. Now both of us have to use the same password and he only has the one account. I have four including his but cannot access the other three. Also when I attempt to create a new email account for my husband the account will not save the new account information whether I do it from my email sign in or his email sign in. The primary account information is my name, his email, but I have disabled his email and need to create a new one for him that isn't merged with my primary email account.