I regret to say there is no good treatment for congenital myopathy. The nature of your myopathy is unclear. Some myopathies show anticipation i.e. the next generation gets disease earlier than previous but it is unlikely you have one of those. I fear there is no treatment and we cannot predict when you will get severe problems. By your history it is likely that about half your progeny will get the abnormal trait. All those with the trait may not get the symptoms.