You should talk to him about it without being accusatory. If neither of your views change you can see if there’s a compromise when it comes to talking about them, storing them, or carrying them. Like maybe he doesn’t do it around you. If neither of you are willing to compromise then that could lead to bigger issues tho and it may mean there’s other people you’re both more compatible with.
DV aside you’re not automatically safer just because someone has a gun either. There’s also an increased likelihood of accidents, risk taking behavior, or having it used AGAINST you by a threat. Not to mention how panic can cause the weapon to be misused. Whether having it makes you safer entirely depends on how the person with it acts, talks, and how intense their training is. To me I’m safe with my dad with one. But my sister? Hell nah!
As someone who’s had to take safety courses myself you get what you put into them. You can breeze through those and not have anything stick past the test if you don’t want. And it doesn’t always include intense training in high stress that would actually happen in an emergency. So how much work he’s putting in and talking about it is definitely a factor. I know people who’ve taken those courses that I still wouldn’t trust with a gun, especially not in an emergency.