Worst thing he could do is leave the house. He must stay in the house.
Well couples sometimes argue a lot, then it’s over. But I agree with GLA, if he suspects papers are being drawn up under no circumstances should he move out or even look at another place to live until ordered by a judge.
But that “I don’t feel safe” stuff is a little bit psychobabble and used for dramatic effect. Women generally do need to feel safe but I presume he gave her no reason to feel genuine fear, that he isn’t physically abusive or fall down drunk all the time. Just a “card” to play in the argument as the OP said.