Annie, I remember you have asked about a Chromebook in the past as well as disliking Microsoft Windows 10. I'm not sure that trying different operating systems is going to help you. You could buy a separate keyboard to go with your iPad and you would, for most purposes, have the equivalent of a Mac. (Mac aficionados, please don't tell me the difference, I do know).
Do you think using a keyboard will help your hands? Have you tried 'splitting' the virtual keyboard on your iPad and just using your thumbs, would that help?
Before spending any more money, if I were you, I would try and get some help either by phone or through a home visit, a quick 'Google' brought up the following:-
www.abilitynet.org.uk/find-abilitynet-volunteer
It may be better to come to terms with Windows 10 and add some additional software that would make dictation simpler. These are just my thoughts for what they are worth.