Good job. To be completely honest, you did better than I expected. With some proper training, the sky is the limit for you.
As for the cramping issues, a lot of that would be taken care of with better training. More miles on the legs will build your ability to handle the stresses of running for so long in one morning. Also, cramping can be caused by race day issues like electrolyte imbalances (make sure you are taking sports drink or using gels when you take water) or pacing (your pace got a little hot around miles 3-5, this could have taken its toll on you later).