To be completely honest, I think this is going to be better asked to a physician who is more familiar with your specific challenges. At the end of the day, every restriction and requirement I set out for students - drawing from their shoulder, not leaning on their elbows, etc etc etc. gets thrown into the wind when we start taking physical disabilities into consideration. While I have to be pretty firm with people who don't have diagnosed disabilities that the muscle exhaustion they experience after drawing from their shoulders is normal, that we are pushing ourselves to do things in a way that inevitably will be uncomfortable for us, simply because people have a tendency to think themselves uniquely unqualified for the tasks, your situation is fundamentally different.

Talk to your physician and find out what kind of stress your body is going to be okay with, and what might actually be harmful for you in the long run. If drawing from the shoulder is simply not an option for you, then that changes things - it means you'll be drawing from the elbow at best, and suddenly anchoring your elbow on the table by leaning on it becomes a useful approach, rather than something to avoid.

Always remember that you are going to have to be extra patient with yourself, and accept that because your situation is more unique, there will be "rules" that simply cannot reasonably be applied to you. This doesn't mean you can't draw, but it does mean that there will be new strategies you'll have to come up with along the way for yourself, and that these more generalized frameworks won't necessarily apply to you in every possible way. There's still plenty of value here for you, but don't hurt yourself while trying to conform to every little bit.