Hello, ROBL14.
Thank you for posting in Apple Support Communities. It sounds like you and your husband are experiencing an issue where he is using your old iPad, and it keeps asking to log into an old Apple ID. You mentioned that you try to go into the Mail account to make changes, but it becomes unresponsive and that your current iCloud account has been locked for security reasons.
We’d like to try and help you unravel the issue you’re experiencing a piece at a time.
First, if you’re being prompted that your account has been locked for security reasons, you may need to reach out to Apple directly:
If your Apple ID is locked or disabled - Apple Support
Generally, when you see the prompt for an Apple ID that is no longer being used on the device it’s because there are apps that were originally downloaded with a different account. If you see the prompt when an app tries to update, delete the app and download it again. Note that you’ll need to make sure you resolve the issue with your Apple ID before trying to download an app.
Warmest Regards.