Why are you still trying to fix your ex's problems?
If his dad is 75 years old and in ill-health what possible good could come from dragging them into this nightmare. He obviously cant help him and it would just make his last years even more difficult. If they do ever find out in their lifetime then it would be best if they found out on their own. there seems to be no benefit at all with burdening them with their son's problem.
Instead why not sit down and write out three problems in your own life that you would like to solve and go to work on those.