I have cerebral palsy on my left side, so I feel your pain..
What I do is use a Logitech 3d extreme pro and xpadder.
I can map 1-8 on POV and surrounding buttons, use trigger as shift to access 2nd bar. Directional is obvious.and misc mapped on the base buttons (I have tab mapped on first button that my left thumb can tap). With this, I can successfully play game with just my right index finger and thumb and left thumb.