Very, very low. Assuming the fracture healed completely and in an "appropriate" position, it is very unlikely that you will re-break your wrist. It often takes 6-8 weeks for fractures to heal and an additional 4 weeks to regain normal bone strength. However, low bone density can increase your risk of re-fracture. Radiographs are necessary to determine the strength of the bone following injury.
Repeat injury. In the post injury. As always more likely to occur at the site of the original injury so the likelihood of fracturing again in the same place is higher however one cannot worry about having 90% of the force causing a fracture because the force thatit took two caused the fracture was fairly great and doesn't occur very often as one gets away from the injury the likelihood goes down.
Healing. Once healed, you would need another injury of equal severity for it to break.
Not likely. Just because you broke a bone once and it heals correctly, your risk is not usuaqlly increased.