I think it will be diffcult for people to make a specific recommendation for equipment that would work for you.
99.9% of the devices on the market are designed for people that have full control of their hands. Also the vast majority of CAD users have full control of their arms/ hands and often it it difficult for us to imagine what limited control of those extremities mean.
For my Mechatronics Masters thesis (25 years ago) I designed a device to precisely measure the movement range of the main joints in the arm and hand, particularly aimed at people that were very strongly handicapped, e.g could not lift their arms and I have some limited understanding of this subject.
If you're comfortable with it, have someone take a video of you operating a computer so your hands and theit limitations can be see. You'll likely receive much better response.
Also, i really see no reason why voiced control should not be a possibility, particularly when working with an iMac. It will certainly not eliminate the need for pointing devices, but would provide tremendous benefit in reducing the number of mouse moves and clicks a user has to make.
I,ll put this into the Ide Station right after completing this post.
Peter Doering