I think your treatment is not going the way it should be. I would like to see your both X rays. If possible.
You need to remove cast as most fracture healed by this time. And as you are saying that your hand is numb then it is dangerous to keep cast. May be it is pinching some nerve
for your tail bone fracture
i have following advices.
1. Sit on soft surface and not hard, avoid prolong sitting. If you have to sit for long take a ring like cushion so tail bone remain pressure free.
2. Sit in a tub filled with gentle warm water daily.