I believe these questions could be answered much better by a qualified professional, such as your rehab and/or physical therapist. There are some Accessibility options - look in System Preferences > Accessibility - but we are only other users helping to use Mac products, not professionals. I'd take either/both to my next appointment and ask them to help me use them (after looking at the possible options in that Accessibility Pane). These people would know exactly what it is you should or need help with, so I think that would be your best option. If you do not currently have someone like that, I would ask my doctor and say "I need help with using my computer because I can't......... - is there anyone you can send me to"
Much luck in your efforts; glad you can actually write here and ask!