Evil my mum never left my dad because she was scared of him (was a lawyer) and she didn't want to lose the lovely (scary) house and all her things (read, freaky antiques). We would have been so much happier without his emotional abuse, but she never dared do it.
N is young now, but in a couple of years if you didn't leave would so pick up on your dp's attitude to his mum. Unhappy parents lead to enormous scars. I know that people whose parents broke up talk about how hard it was. But those of us whose parents stayed together are left with amost irreparable scars too.
I am sure that some of my very nasty relationships lasted too long because I just didn't realise what a normal relationship should be. Realisation of thathas made me massively stronger in my current relationship. First sign of nastiness and my flight instinct kicks in. Luckily onlytwice in 7years (we all have ups and downs).
Don't let yourself be the past me, or my mum, which is the extreme example of the past me. Your DP can threaten you with all kinds to make you stay, but you don't have to. It won't work. You're about to teach your son, like chasing is doing, that women deserve respect. Because your DP isn't teaching him that.
Lecture over. I hope it helps and doesn't comeover as hectoring bollocks 
And yes, anything you need, quiche is here. Really.