That sucks, sorry to hear about your problem
It's not quite the same, but Michael Perry lost his right hand and had to learn to sculpt with his left. It may be worth seeing what he has to say on the subject.
As for holding the miniature, can you grip it at all? There are arm rests that would probably let you position your arm, eg
Setters Arm Rest. I've watched a painting video with Jen Haley using two to support her arms while painting.
Failing that, there are vices available with ball joints, but repositioning the figure is going to really slow you down.
ball joint vice. However, they are not cheap
I do have the Draper vice, but it doesn't grip as tightly as it should, so things can move if I push too hard.
As the others have said, practise writing with your left hand. For painting, I'd be tempted to start with buildings or vehicles and work down from there.
Good luck