Understanding Sin as a Disease

Questions about how we can be guilty when we sin if sin is a disease we’re born with, how it can be that we’ll have free will in Heaven but not have the ability to choose to sin, and whether morality and logic are correct because God says so or he says so because they’re correct.  

• If sin is a disease we’re all born with, how can we be guilty when we sin?
• Can you explain how we will retain free will in Heaven but will not have the ability to choose to sin?
• Is morality correct because God says so, or does he say so because it is correct? Is logic correct because God says so, or does he say so because it is correct?