The radial nerve controls elbow, wrist, finger and thumb extension but the most obvious sign of radial nerve injury is 'wrist drop'. Extension of the thumb is done by a group of muscles, which is innervated by posterior interosseous nerve (branch of radial nerve). In radial nerve injuries this nerve recovers the last and that is the reason you are having difficulty in thumb extension. I think within the next 8-10 weeks you should start seeing recovery of this group of muscles of the thumb. Till that time you should continue to do physical therapy of the wrist and thumb to keep the joints supple.
Regarding the elbow, I think you are suffering from posttraumatic stiffness. I would advise you to get rid of the elbow pouch, as this will only increase the stiffness. You should see a physical therapist who can work on improving the range of motion in your elbow. It might take several weeks before you can fully straighten your elbow.