Technically he's right on the encryption part,
What? That doesn't make any sense. Please explain.
My father-in-law who works for a computer company found out last week that I was getting a miner and has now convinced my wife that this is a scam and that I'll be helping to destroy encryption.
Either your wife accepts your knowledge after extensive research about what you are doing, or she accepts her father's opinions after no research at all.
If she chooses to accept her father's uneducated opinion over your educated facts, then you need to figure out how to communicate with your wife in a way that will lead to a harmonious marriage. Only you know her personality well enough to do that.
Any ideas, or articles or sites that I can show him to make him realize that he's incorrect in this area and make my home life much better than it is currently?
Your father-in-law clearly has no interest in understanding anything about bitcoin or he'd be asking questions instead of making uneducated declarations. As such, showing him articles or sites isn't going to accomplish anything. His mind is made up, and any site or article you show him will likely be dismissed as "propaganda".