The best way to get past this is education, both for you and your father. Your father needs to get training to really understand and internalize gun safety. He needs to understand the huge responsibility of owning firearms. He needs to understand the rules of safe ownership, storage, and handling and also get coached in shooting so he understands it ain't like in the movies - the odds of him hitting the broad side of a barn, let alone an intruder are pretty slim without thousands of rounds of practice of correct technique. The NRA (safety and education arm, not legislative arm) offers a basic pistol class which is step one for any owner. That class does very little actual shooting but instead is mostly classroom time dedicated to understanding and safety. That might help him come to the realization that a gun is not necessarily the best tool for the job and comes with more responsibility than he's willing to take on. While I own dozens of guns and no longer have kids at home, all of them stay locked in a safe because I personally don't want to get into a gun fight in my house. I shoot enough to know there's more potential downside than upside to it. That's just my personal perspective.
It's probably worthwhile for you to get some training too so you can change your fear of guns into respect for them. Respect for something dangerous based on knowledge is a lot more useful than fear.