ipad account(s)

My iPhone is setup under one email address and I had an iPad also setup under that same email. My husband got an iPhone and so I created a new email address for him to have for his phone, etc. since I also used my phone for work and didn’t want to cross profiles, etc. I eventually got rid of the iPad and got a newer one. I removed the old iPad from my account but for whatever reason I couldn’t get the new iPad added to my own email address so I put it under his Apple (email) profile. Now I want to have my phone and iPad on one Apple profile (vs two) but the iPad doesn’t let me update any of that information saying “email address in use” type message.

How do I get my iPhone and iPad under one Apple profile? Do I have to reset/wipe the IPad and start over? What a colossal pain that would be. Please give me some direction.

Thanks.