When it is permissible to leave one's wife

Specific situation: wife has mood swings, most of the times she treats me well but at night an occasional "Fiona mode" happens, and I don't mean the physical appearance. I tell myself she's exhausted breastfeeding a 30 month old toddler (of ours), but I vaguely remember the instances of mean reaction to my nightly advances before our second kid was born. And she regularly (a few times a week) lashes out at our older kid. So the question I ponder do we have a relationship. Is that a woman that's worth my while. And if we don't then why staying. Not sure if this is an opinion based question.