How can I improve my iOS security settings?

You have already used the available additional measures to protect your AppleID from compromise by someone who gains unauthorised access to your iPad.

The one additional measure that you should consider is the email address that you provide when initially setting the ScreenTime Passcode - as this email address is used to reset the ScreenTime Passcode if it is forgotten. When setting this recovery email address, you should choose an email address that is not used to identify your AppleID account (which is often your primary email address).

If you need to change/reset the email address associated with your ScreenTime Passcode, you will first need to remove the ScreenTime Passcode - and then set a new Passcode:

Settings > ScreenTime > Change Passcode ScreenTime Passcode > Turn Off ScreenTime Passcode

When setting a new ScreenTime Passcode (which can be the same as used before), you will be prompted to provide an email address that can be used to reset a forgotten/unknown ScreenTime Passcode. As already outlined, for your security, you should use a different email address to that used for your AppleID - or, should you choose to do so, you can skip this step entirely and not set a recovery email address at all.

If you choose to not provide an email address to recover a forgotten ScreenTime Passcode (this being the more "secure" option), be sure to know and/or record your Passcode somewhere safe - as without a recovery email address to receive reset instructions, the only way to recover is to fully reset the iPad to factory settings; in this situation, you will not be able to restore an iCloud or iTunes backup - as the backup includes the unknown ScreenTime Passcode.

As for additional measures protect your AppleID account from compromise, iOS for iPhone includes a new feature known as Stolen Device Protection. For some inexplicable reason, given that iOS and iPadOS share the same code-base, Apple have not released this essential security feature for iPad:

About Stolen Device Protection for iPhone - Apple Support

Use Stolen Device Protection on iPhone - Apple Support

Apple does invite submission of comments and feature requests via its Product Feedback portal. If you would like Apple consider releasing this essential security enhancement for iPad, this would be the most appropriate channel through which to submit a request:

Feedback - iPad - Apple

Every submission counts. Until Apple receive sufficient number if requests for this feature, Apple are perhaps unlikely to make this essential change.

As is, when a bad actor has opportunity has access to both an iPhone and iPad of a victim, the iPad allows far easier access to the AppleID account of the victim. Road warriors that carry and use both iPad and iPhone when travelling or away from home are at obvious risk of this flaw in Apple's current security posture for these devices.

You are very welcome.

Beware of using an account alias for your ScreenTime Passcode recovery. If your ScreenTime Passcode recovery uses an alias email address that links to your AppleID, you will defeat the entire purpose of using a different email address...

The objective is to avoid sending reset email to the AppleID email account that will be directly accessible form the device that you are attempting to protect with additional security measures.

Equally critical is the supplementary advice outlined within my second reply - concerning the need to ensure that you do not save your AppleID account credentials in your Apple Keychain.

Continued...

A further step to avoid potential compromise of your AppleID account is to ensure that you do not have your AppleID account credentials saved to your Apple Keychain. If this credential needs to be recorded, for your security, it should be securely saved elsewhere (e.g. an entirely separate Password Manager - such as Bitwarden).

As you are doubtless aware, for iOS/iPadOS 17 and earlier, your Passwords are accessed from your device settings; for iOS/iPadOS 18, saved Passwords are accessed using the new Apple Passwords App.

As your saved Passwords can be accessed using just your device Passcode, all your account credentials (including your AppleID account credentials if saved here) can be easily accessed by anyone that has your device Passcode.

Among other measures introduced with the Stolen Device Protection, this feature prevents access to saved Passwords using just a Passcode when you away from a location that you frequently visit.