For me the danger of all these externalities outweighs the potential gains.

The biggest danger of all is the perception that you are somehow in control of things that you can mitigate but do not actually control.

While you may be correct that spousal conflicts are not the biggest cause of deaths, a quick search showed that suicide is 5x more likely if that suicidal person has access to a gun.

Whether you get along with your spouse today is not guaranteed tomorrow. Counseling? Yes it helps. Guns? Statistically not.