11 Year Old Son with Confusing and Troubling Signs of SPD

We have an 11 year old son, diagnosed as moderately dyslexic,who also shows many signs of ADD and now I am thinking SPD as well. He is a gifted athlete, extremely high intelligence. He recognizes that he is hypersensitive to sounds, and takes appropriate measures. The area which poses the most significant problems for our family are his meltdowns prompted by transitions, changes in plans, etc. (He manages to hold it together at school, but often falls apart when he comes home.)These explosive reactions can result in extreme tantrums that can be the undoing of an otherwise pleasant experience, and which can affect the entire atmosphere in our family. I don't know how to help him with ways to accommodate these inevitable occurrences. Help!