What goes on between a husband and wife is their issue as long as they consent, which by the illustration in the movie, they did.
The discussion about gun safety is a different one, and I suspect we would agree on that.
But healthy or unhealthy was not what I was thinking when watching that scene. In my opinion, it was a statement that Chris Kyle was making progress back closer to what he had been before four tours of duty in a war zone.
Pointing a gun at anything you do not wish to destroy is a Cardinal rule.
I saw the scene as both of them having PTSD themselves.