I had PND after both DC, I look back now with a clear head and realise it was exacerbated by his behaviour. My second DC had health issues meaning he woke every hour until he was two and half. I worked full time and did all of the waking as he slept through them and the rare time he did get up caused more issues.
This is the guy who said I woke him breathing in bed every night and blamed me for him him being tired. I laugh now, he stayed up till after midnight every night but got a solid seven hours of which he would snore so loud that neighbours used to say he kept them up.
Of course it was all my fault, his lack of sleep, DC medical issues that to this day he insists I mostly made up, me being so tired for sex...
Why did I stay? I honestly can't answer, but please don't inflict this man on a child. They don't have a choice, you do.
A lot of times after he birth of a child it's harder for them to hide their behaviour. He is like his before a child, take the warning.