Which cardiomyopathy does he have? There are 4 types; Dilated (where the heart enlarges), Hypertrophic (where the heart muscle thickens), and the two others are rare- restrictive and arrhythmogenic. I'll assume you mean dilated cardiomyopathy
as it's the most common.
1) There is no actual treatment, just management. Medication eases symptoms and prevents other complications for occurring.
2) Medication will generally prevent heart failure
and other symptoms. Only in severe cases ( if medication fails to control symptoms) is a heart transplant considered. If there is only mild enlargement of the heart, then your son may not have any symptoms at all.
3) Again it depends on how much this has affected your child, complications as a result of dilated cadiomyopathy are blood clots
, arrhythmia's and in some cases sudden death. Providing medication controls your sons' symptoms and prevents heart-failure, it should not interfere with his life too much.
This is really general advise, you need to talk to your Doctor.