This support page may be helpful:
Accessibility - Mobility - Apple
It may also be worthwhile to directly contact Apple Support - and ask to speak with an Accessibility Specialist. Apple have a team dedicated to offering support for all kinds of accessibility issues. They will be able to offer help and support with suggestions and specific settings for users with difficulties with motor function and other disabilities.
You can contact Apple Support using the Support link at top-right of this page. Alternatively, you can initiate contact, or open a support case, using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:
https://apps.apple.com/gb/app/apple-support/id1130498044
I hope this information is helpful in obtaining the specialist help that you need.